We just recently noticed that we are unable to add or modify tags in the designer. Any time a new tag is created from the OPC Browser (which works) or if it is modified, such as adding tag history, the tag will go to the green question mark. Tag diagnostics shows no error, only a null value. Using the OPC quick client, I am able to read tags values which are accurate and change just as they do in the device (AB CompactLogix), but if I try to subscribe to the tag the quality shows as [STALE]null. This problem occurs in all firmwares and drivers (v20 or less, or 21 or higher) and across all devices connected. All existing values are good and reading but if we make any changes to the tags at all, even if we open the tag editor and click OK rather than cancel the tag will go to the unknown or uncertain state.
The obvious thing is to restart the OPC module but that is a big risk for me since everything that is currently configured is working and I’m afraid all my tags will end up going to unknown state.