Firefox 94 when ran from a crontab claims "is already running, but is not responding."

Solution 1:

Your crontab script needs to have the environment variable DBUS_SESSION_BUS_ADDRESS correctly set, ie. to the same value that is used in your desktop session. Myself I use this method for a crontab script that uses notify-send to display notifications on screen. This value is usually static per user, ie. it does not change between sessions, depends only on the user ID, so you may simple copy it from your desktop session to your script. Or to be always sure that you use the correct value, you may put a script into your session startup programs, that writes out this value to a temporary file, and your crontab script reads it from this file.