QjackCtl icon is an Exclamation Mark - No idea why

Hello,

I am trying to set Jack up on my Mint desktop. Haven't managed to get it to work yet.

I reset settings to default and now I have the qJackCtl exclamation mark on my iconbar. The context-sensitive tool-tip just says 'JACK Audio Connection Kit [(default)] Active. (0.64%, 0 xruns)', there's absolutely no hint as to WHY it is in an erroneous state.

Messages say:

18:56:48.505 Statistics reset.
18:56:48.512 ALSA connection change.
18:56:48.567 D-BUS: Service is available (org.jackaudio.service aka jackdbus).
18:56:48.621 JACK connection change.
18:56:48.639 Client activated.
18:56:48.639 Patchbay deactivated.
qt5ct: palette support is disabled
18:57:16.369 JACK connection graph change.
18:57:16.518 JACK connection change.
19:04:22.208 JACK connection graph change.
19:04:27.804 JACK connection graph change.
19:04:29.266 JACK connection graph change.
19:05:24.709 JACK connection graph change.
19:05:33.856 JACK connection graph change.
19:05:41.611 JACK connection graph change.
21:27:00.227 Client deactivated.
21:27:01.572 JACK connection change.
21:27:01.588 Client activated.
21:27:01.588 Patchbay deactivated.
21:27:01.707 JACK connection graph change.
21:27:13.056 JACK connection graph change.
21:27:35.698 Statistics reset.

I tried searching but there seems to be a new company called "Jack'd", which Google now thinks I am talking about even though I didn't type an apostrophe pmsl Google always 'knows better', eh? ffs

Anyone know why the icon is an exclamation mark? Also, just for some insight into modern software development issues, are my expectations of some visible error information from the software too difficult a concept to accept nowadays?

Also, is there any up-to-date, accurate documentation for a Jack-based set-up with Ardour on Mint or, again, are we expected to guess correctly, nowadays?

Many thanks for any information.