Multitrack arm for record greyed out in all tracks
I'm recording Multitrack sessions on Audition CC2018 and from being fine in one session, suddenly all the "arm for record" buttons appeared greyed out in all tracks when I opened a different session - and now the problem is there in all sessions. It won't allow me to arm any tracks to record on them - I can do everything else, but not record.
The microphone works fine and I can record in "Waveform" mode - but not in a Multitrack session.
I have tried the usual re-starting computer, etc, but the problem persists. Please help!
UPDATE:
If I create a new empty Multitrack session, that new session works fine. If I open an already created session which already has recorded audio files in it, then sometimes it works fine, most times it does not - I have not been able to find a pattern (some were recorded some time ago, some are new). In the sessions that have the problem this window (which I had never noticed before) appears while the session is loading:

Also, If I create a new Multitrack session while I have a problem session open, the new empty session works fine and when I switch back to the problem session the arm to record buttons are available and work fine - but not always; sometimes this works, sometimes it doesn't.
