I'm sorry you're having trouble. Sounds like you'll get to contact support so they can try to reproduce that issue here (support @ opto22.com is always the best way to contact them).
A few questions/comments for you that you should also let them know the answers to:
- Normally you shouldn't see that "missing tags" message unless the device has been deleted. Is the OPC-UA server "device" still in there? (Under Configure > Devices & Tags?)
- Are you using the just-released R3.0[B]b[/B]? Or R3.0a? (If you don't already have R3.0b on there, I'd back up the project and upgrade to see if that helps.)
- If you look under: Help > View logs do you see anything relevant-looking? (You could download those logs and send them to support while you're at it too.)
I hope you'll let us know how it turns out!