It usually means it bugged out

The current 3.11.x releases of patchwork have some issues when switching versions. This will hopefully be fixed in the next release (3.12.0) coming very soon.

The problem was with the scuttlebot server that 3.11.x uses. It needs to regenerate the indexes, but it is not notifying patchwork when it is done and safe to load again. What I found worked was waiting about 2 minutes of "scuttling" and then restarting (CMD+R or CTRL+R or just close and restart the app).

Anyway, hopefully won't be a problem after the next release!