I had a session open and I clobbered JACK.
(Nothing to do with the recording session…was tinkering in a terminal window.)
At which point I was able to resurrect JACK. But, Ardour wouldn’t let me close the session. (it would allow me to quit though)
When I started Ardour, chose the session that was open all was good.
My question is: is there a way to reconnect to JACK without shutting Ardour down?
I didn’t see a way to get to the Ardour start up dialog that lets you select the back end in a running session.