OPC uncertain_lastknownvalue but all reads are good

Ignition
1

I'm trying to connect to a nonlocal opc server, and the connection is forming (says connected in the admin page), quick client reads look good, but quick client subscriptions and actual opc tag subscriptions all give uncertain_lastknownvalue. I've confirmed the OPC server works on other applications and a local copy of the same opc server codebase and config works with ignition. the error in the logs is OpcUaSubscriptionManager

05Jun2026 12:10:04

onWatchdogTimerElapsed()

over and over again.

Any advice? glad to attach other diagnostic logs.

2

Try setting the tag group to "read" instead of "subscribed". If that yields live values, then you likely have a broken OPC Server implementation. Broken ones are fairly common, if topics on this forum are representative. If you cannot share the brand/version of the server here, open a ticket to get private guidance.

3

Thanks!

(Locally written OPC server based on open62541 I use for some testing, which worked on windows, but the linux/docker builds are failing. Debugging internally, but the read to subscribe fix helps me debug!)

4

@pturmel lol, you'll like this. It was a bad gcc optimization choice (-funroll and -O3, needed to swap to -O2 . apparently that breaks open62541)

(the moral of the story is 'homerolling OPC server implementations for local testing leads to new and intriguing failstates')