# Modbus tcp tags not working **URL:** \ **Category:** General Discussion\ **Created:** [September 11, 2020, 6:20pm UTC](https://forum.inductiveautomation.com/t/modbus-tcp-tags-not-working/38604 "2020-09-11T18:20:40Z")\ **Posts on this page:** 2\ **Page:** 1
**Author:** ![DAVID.RIISKA](https://avatars.discourse-cdn.com/v4/letter/d/ed8c4c/32.png) [@DAVID.RIISKA](https://forum.inductiveautomation.com/u/DAVID.RIISKA)\ **Post date:** [September 11, 2020, 6:20pm UTC](https://forum.inductiveautomation.com/t/modbus-tcp-tags-not-working/38604/1 "2020-09-11T18:20:40Z")
Im having an issue with some Modbus tcp tags im getting from a compressor PLC. I have 3 identical compressors. When I first mapped the addresses of the first compressor they came over just fine but after doing the other 2 compressors a little different I deleted the tags from the first compressor and tried to re- map them the same way I did the last 2. The issue is the first compressor tags show up with a question mark and an uncertain initial value error. The device is connected and there are no errors other than when I add the tags from that compressor they all have a (?) as the value. The other 2 compressor tags are fine. I have tried to delete and re add the tags, delete and re-do the device connection, but nothing seems to work. Any Help would be much appreciated. Ignition version 8 Thanks Dave ---
**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:** [September 25, 2020, 9:48pm UTC](https://forum.inductiveautomation.com/t/modbus-tcp-tags-not-working/38604/2 "2020-09-25T21:48:37Z")
Can you share a screenshot of the mapping for the problematic connection? Did you delete all the tags you created in Ignition Tag Browser and re-drag them in from the OPC Browser after you changed the mapping?