I can confirm that I too have this problem on usegalaxy.eu with Interactive JupyTool and notebook.
When I tried to load a previous notebook yesterday (23rd April 2024), then it took hours to see a response, and ultimately the notebook often started in a stopped state. The tags on the right-hand History panel remained grey, neither yellow nor green.
Maybe my problem is that only one notebook at a time by one user is allowed* and I started multiple, so each new one was automatically prevented from running.
*See here:
Now I shut down the running one. Thereafter very quickly a stopped one started running. I stopped that too. A new stopped one started. This way I could deal with the stopped ones by shutting them down one after the other.