Thanks for the screenshot! What's happening here is the AI Assist context window is getting too large to process, and when it tries to summarize the thread to make room, it can get stuck in that frozen state.
A couple of things to try to get you unblocked:
Start a new Assist thread: start a fresh conversation
Hard refresh after that
That should do the trick! If it keeps coming back, it's likely your app has grown pretty large, breaking it into smaller apps tends to help keep Assist running smoothly long-term.
I've gone ahead and added your +1 to our internal ticket for adding a clearer error message here so it doesn't just silently freeze, appreciate the report!
Let me know if the steps above help you get unblocked!