@lambdat75 I had this problem and then someone said it works if you log in directly on the web page. Never had a problem since and it's been several months. Here is what worked:
Well it took a while but I figured this out. Not sure why nobody at Opera can answer the question.
Turns out the problem is GPU acceleration is the problem. Turning it off fixed it. But not until I had completely uninstalled and reinstalled Opera and found that didn't fix it. It had started with the update before the most recent, for some reason.
So for anyone else running into this, turn off GPU acceleration.
@sgunhouse Thanks, it's enabled. I was able to get another extension (calculator) to load in the sidebar, so it's just Bitwarden. Maybe I need to ask them, but it did work before.