# \[IGN-13789\] \[null, Bad\_NotConnected("Communication with the data source is defined, but not established, and there is no last known value available."), **URL:** \ **Category:** Ignition 8.3 Early Access\ **Created:** [July 30, 2025, 7:33am UTC](https://forum.inductiveautomation.com/t/ign-13789-null-bad-notconnected-communication-with-the-data-source-is-defined-but-not-established-and-there-is-no-last-known-value-available/109125 "2025-07-30T07:33:09Z")\ **Posts on this page:** 13\ **Page:** 1
**Author:** ![gareth.lovell](https://avatars.discourse-cdn.com/v4/letter/g/3d9bf3/32.png) [@gareth.lovell](https://forum.inductiveautomation.com/u/gareth.lovell)\ **Post date:** [July 30, 2025, 7:33am UTC](https://forum.inductiveautomation.com/t/ign-13789-null-bad-notconnected-communication-with-the-data-source-is-defined-but-not-established-and-there-is-no-last-known-value-available/109125/1 "2025-07-30T07:33:10Z")
HI All, pinged ok to PLC. Siemens S7-1500 connection established in OPC in the gateway. No errors in the log. S7-1500 setup as symbolic, not absolute. Browsed in designer and found the blocks and tags. Have "Bad\_NotConnected" on the values of the tags. The timestamp is from when the PLC is first connected but then data isn't being repolled or refreshed. The error on the data is: [null, Bad\_NotConnected("Communication with the data source is defined, but not established, and there is no last known value available."), Wed Jul 30 16:41:18 ACST 2025 (1753859478154)] Is there something obvious I am missing here? Regards, Gareth ---
**Author:** ![Kevin.Herron](https://sea1.discourse-cdn.com/inductiveautomation/user_avatar/forum.inductiveautomation.com/kevin.herron/32/7259_2.png) [@Kevin.Herron](https://forum.inductiveautomation.com/u/Kevin.Herron)\ **Post date:** [July 30, 2025, 11:19am UTC](https://forum.inductiveautomation.com/t/ign-13789-null-bad-notconnected-communication-with-the-data-source-is-defined-but-not-established-and-there-is-no-last-known-value-available/109125/2 "2025-07-30T11:19:43Z")
I had this problem as well when I dragged all the tags in from one of our S7-1500s... if you set the "drivers.SiemensSymbolic" logger(s) to DEBUG do you start seeing a message like this in the logs? ```python DEBUG SymbolicAddressSpace 30Jul2025 04:17:34 read: read call failed: AGL40_SYMBOLIC_NOT_APPLICABLE de.deltalogic.accon.aglink4.AglIOException: Method: 'symbolic_CreateAccess', Error Code: 'AGL40_SYMBOLIC_NOT_APPLICABLE', Error Nr: '0xFFFA0000', Error Message: 'AGL40_SYMBOLIC_NOT_APPLICABLE', ``` for me there seems to be one or more "bad" tags somewhere that bring the whole read request down. Anyway, the right developer should be taking a look at it today. ---
**Author:** ![Cody\_Morgan](https://avatars.discourse-cdn.com/v4/letter/c/db5fbb/32.png) [@Cody\_Morgan](https://forum.inductiveautomation.com/u/Cody_Morgan)\ **Post date:** [July 30, 2025, 4:14pm UTC](https://forum.inductiveautomation.com/t/ign-13789-null-bad-notconnected-communication-with-the-data-source-is-defined-but-not-established-and-there-is-no-last-known-value-available/109125/3 "2025-07-30T16:14:36Z")
As Kevin said, I'm looking into a similar issue today. If you could check the debug logs, it can help confirm if this is the same issue or something different. ---
**Author:** ![gareth.lovell](https://avatars.discourse-cdn.com/v4/letter/g/3d9bf3/32.png) [@gareth.lovell](https://forum.inductiveautomation.com/u/gareth.lovell)\ **Post date:** [July 30, 2025, 10:39pm UTC](https://forum.inductiveautomation.com/t/ign-13789-null-bad-notconnected-communication-with-the-data-source-is-defined-but-not-established-and-there-is-no-last-known-value-available/109125/4 "2025-07-30T22:39:05Z")
No problem, I will check the debug and report back in this stream ---
**Author:** ![gareth.lovell](https://avatars.discourse-cdn.com/v4/letter/g/3d9bf3/32.png) [@gareth.lovell](https://forum.inductiveautomation.com/u/gareth.lovell)\ **Post date:** [July 31, 2025, 12:21am UTC](https://forum.inductiveautomation.com/t/ign-13789-null-bad-notconnected-communication-with-the-data-source-is-defined-but-not-established-and-there-is-no-last-known-value-available/109125/5 "2025-07-31T00:21:18Z")
Hi Cody and Kevin, I have uploaded two log files with debugging. Our team helped with the diagnosis. Gateway We did some standard data connection testing with disabling the S7 OPC connection, then removing the cable etc. No joy. "Bad\_notconnected" and the timestamps were not updating. This is the log A file and was downloaded with a timestamp of 0859. Designer We then removed the groups of tags we had previously dragged over and started with some specific tags and added them individually. This was good and provided good data transfer. Not particularly important but these were alarm tags that we were able to toggle the "test\_alarm" tag and trigger the other alarm tags we added. We added some global clocks, and they worked ok. We then dragged the folder of tags from yesterday and broke it (somewhat deliberately). Daniel (much more experience than I) sorted through this folder and with a couple of trial-and-error attempts found a tag that assigned as a "String" datatype that is not designed as a string datatype in the PLC. Daniel removed this tag and the whole folder of tags communicated correctly. We confirmed good timestamps that were updating. This is LOG\_B. We are working out the original datatype of the tag that caused the break. Hopefully the logs are helpful. [Logs redacted] Regards, Gareth I've edited this post to redact the log files in case there is any sensitive information there. I have them downloaded and will review them tomorrow. -Cody ---
**Author:** ![Cody\_Morgan](https://avatars.discourse-cdn.com/v4/letter/c/db5fbb/32.png) [@Cody\_Morgan](https://forum.inductiveautomation.com/u/Cody_Morgan)\ **Post date:** [July 31, 2025, 1:11am UTC](https://forum.inductiveautomation.com/t/ign-13789-null-bad-notconnected-communication-with-the-data-source-is-defined-but-not-established-and-there-is-no-last-known-value-available/109125/6 "2025-07-31T01:11:56Z")
Thanks Gareth! This is very useful. I'll take a look at the logs in the morning. ---
**Author:** ![gareth.lovell](https://avatars.discourse-cdn.com/v4/letter/g/3d9bf3/32.png) [@gareth.lovell](https://forum.inductiveautomation.com/u/gareth.lovell)\ **Post date:** [July 31, 2025, 1:22am UTC](https://forum.inductiveautomation.com/t/ign-13789-null-bad-notconnected-communication-with-the-data-source-is-defined-but-not-established-and-there-is-no-last-known-value-available/109125/7 "2025-07-31T01:22:30Z")
No problem. ---
**Author:** ![Cody\_Morgan](https://avatars.discourse-cdn.com/v4/letter/c/db5fbb/32.png) [@Cody\_Morgan](https://forum.inductiveautomation.com/u/Cody_Morgan)\ **Post date:** [July 31, 2025, 2:57pm UTC](https://forum.inductiveautomation.com/t/ign-13789-null-bad-notconnected-communication-with-the-data-source-is-defined-but-not-established-and-there-is-no-last-known-value-available/109125/8 "2025-07-31T14:57:30Z")
After looking through your logs, I've found that this is a similar but separate issue from the one Kevin referenced earlier. Unfortunately, this issue seems to be the fault of the third party library we are using. An exception is being thrown during the read call, but the "error" message returned is `AGL40_SUCCESS`. With the issue that Kevin referenced, the failure is reported by the library in a tag-specific manner. I have already drafted a PR to handle this issue. However, for the issue you are seeing, the library does not make clear what the issue is, let alone which tag has an issue. > We are working out the original datatype of the tag that caused the break. Any info about this tag on the PLC that you can get me will be very useful. I'm going to attempt to repro so that I can get some more information to the vendor about this issue. If you need a place to upload files related to this issue, feel free to use this dropbox file request: > **[Dropbox](https://www.dropbox.com/request/ilZgcCn8hJgcWdrPPEfi)** ---
**Author:** ![gareth.lovell](https://avatars.discourse-cdn.com/v4/letter/g/3d9bf3/32.png) [@gareth.lovell](https://forum.inductiveautomation.com/u/gareth.lovell)\ **Post date:** [August 4, 2025, 5:20am UTC](https://forum.inductiveautomation.com/t/ign-13789-null-bad-notconnected-communication-with-the-data-source-is-defined-but-not-established-and-there-is-no-last-known-value-available/109125/9 "2025-08-04T05:20:54Z")
Hi Cody, I will get this info from our system people. Dylan and Daniel should be able to help me with this and I will update you. regards, Gareth ---
**Author:** ![Cody\_Morgan](https://avatars.discourse-cdn.com/v4/letter/c/db5fbb/32.png) [@Cody\_Morgan](https://forum.inductiveautomation.com/u/Cody_Morgan)\ **Post date:** [August 13, 2025, 9:50pm UTC](https://forum.inductiveautomation.com/t/ign-13789-null-bad-notconnected-communication-with-the-data-source-is-defined-but-not-established-and-there-is-no-last-known-value-available/109125/10 "2025-08-13T21:50:13Z")
Hey Gareth, no rush on my end. However, my current focus is looking at issues similar to this one. Any info you have about the problematic tag could help. ---
**Author:** ![Daniel\_Bieman](https://avatars.discourse-cdn.com/v4/letter/d/edb3f5/32.png) [@Daniel\_Bieman](https://forum.inductiveautomation.com/u/Daniel_Bieman)\ **Post date:** [November 10, 2025, 4:03pm UTC](https://forum.inductiveautomation.com/t/ign-13789-null-bad-notconnected-communication-with-the-data-source-is-defined-but-not-established-and-there-is-no-last-known-value-available/109125/11 "2025-11-10T16:03:11Z")
Hi, Was this resolved? We are currently experiencing a similar issue when adding string tags from a Siemens S7-1500. Currently on release 8.3.1. ---
**Author:** ![Kevin.Herron](https://sea1.discourse-cdn.com/inductiveautomation/user_avatar/forum.inductiveautomation.com/kevin.herron/32/7259_2.png) [@Kevin.Herron](https://forum.inductiveautomation.com/u/Kevin.Herron)\ **Post date:** [November 10, 2025, 5:05pm UTC](https://forum.inductiveautomation.com/t/ign-13789-null-bad-notconnected-communication-with-the-data-source-is-defined-but-not-established-and-there-is-no-last-known-value-available/109125/12 "2025-11-10T17:05:07Z")
Could be this: [Siemens Symbolic disconnect after adding certain tags - #4 by Cody\_Morgan](https://forum.inductiveautomation.com/t/siemens-symbolic-disconnect-after-adding-certain-tags/110710/4) ---
**Author:** ![Cody\_Morgan](https://avatars.discourse-cdn.com/v4/letter/c/db5fbb/32.png) [@Cody\_Morgan](https://forum.inductiveautomation.com/u/Cody_Morgan)\ **Post date:** [November 10, 2025, 11:40pm UTC](https://forum.inductiveautomation.com/t/ign-13789-null-bad-notconnected-communication-with-the-data-source-is-defined-but-not-established-and-there-is-no-last-known-value-available/109125/13 "2025-11-10T23:40:12Z")
If you're on v4.0.0 and upgrading to v4.0.4 doesn't work, let us know in a new thread. Apparently, there is a similar issue in Siemens Firmware v4.0.4, but only applies when multiple connections are being made. I think the original issue in this thread was something different. IIRC, the way that I was able to reproduce the issue described in this thread was to attempt to read from an Instance DataBlock that contained some tags that were inaccessible. I believe it was fixed in v8.3.1, but we didn't get any confirmation from OP.