On MacOSX 11.6, the Flow feature only works with the user it has been started or set up with. Switching user accounts causes flow to stop working. If you switch back to the original user, it's fine again.

For a sample workflow, one user sets up Flow using Options+. It's working perfectly. Switch users, Flow stops working entirely. The other user can open Options+ app and sometimes you'll get an error mentioning that the background service isn't running (so you can start it) but can't get Flow working for the newly logged in user. In this case, they are both Administrators.

Also tested with a complete logout, but unfortunately the problem persists if it ran on another user first.

If a restart is done, whichever user first logged in is the only one that can use flow.