Hello, it's me again, and this is a really strange one.

So, my full setup: I have an ET200S standing in for an S7-300, it's programmed in TIA Portal, there's a DB with some data that changes.

I have the IOT2040 running Node-Red that reads from it with S7comm nodes, writes them to the flow context, which are then read into an OPC UA IIoT Flex-server's address space.

I also have my laptop connected, I can run UAExpert on it which reads everything perfectly fine and follows the value changes.

I have a TP-700 Comfort HMI configured as the OPC Client, in TIA Portal I can set up the connection, browse the address space when selecting the tag, program starts and connects - but then it never reads the actual values unless it is updated by clicking on for example the home button again, or letting that button go. We get a startup value and it never changes unless there is interaction with the screen.

However... when I connect my laptop and OPC UA to the network of switched ports and start UAExpert and connect and browse the address space, nothing yet happens... but when i click on the tag to monitor so it displays NodeID and such, the value on the competely unrelated (besides being on the same network) HMI client suddenly updates too, just like when I click a touch button on it. If I then proceed to pull that same tag (that is also "monitored" by the HMI) into the middle for constant monitoring, suddenly the HMI's displayed value starts changing with it too! It's as if the HMI as an OPC UA client doesn't actually request the server to send it data unless there is some interaction with the screens, or if something else on the network is already requesting that same data.

I've found a forum post with an eerily similar issue, but that related to OPC DA and a much earlier version of WinCC (namely, it worked just fine in v7.2 but failed like mine in 7.3 or something like that). I have tried installing this project with a v14.0.1.0, v15.0.0.0 and v15.1.0.0 firmware for the HMI, from both a laptop running TIA v15 and a PG running TIA V15.1.

Has anyone come across this / could anyone have an idea what to even start looking at?

Yes, I already tried once and they're not giving support for free.

However, I found a workaround and posting a flow bit for anyone having this problem in the future: a "write" node to constantly read the flow context values and write them into the OPC UA server, thus forcing it to update.