Clicking the freeze button in the Inspector or right-clicking “Freeze Selected Tracks” invokes the freeze menu:
…but pressing OK just closes this window and no freeze is taking place. There are no prompts, no popups and the program appears to be working perfectly fine otherwise.
I am able to freeze channels in existing older projects. However, the freeze function is not working in any newly created projects or tracks.
Interestingly, adding a new instrument track to an older project results in a rather bizarre situation - older tracks can be frozen/unfrozen, but for the newly added tracks in the same project the operation is ignored.
Removing the user settings folder has no effect. Reinstalling Cubase 12 has no effect. Older tracks continue to be easily frozen/unfrozen. Any newly created tracks can no longer be frozen.
Apart from the forced update to Media Bay and a separate Dorico update, I’ve no other system changes in the last month or so.
A comment in the other thread by @rickpaul is exactly what was missing - an instrument track that is to be frozen cannot be empty. Simply drawing an empty MIDI region with a pencil restores the freeze functionality since there is something there now that can be operated on.
This was an insane mental glitch and a huge waste of time. How embarrassing. Thank you @alexis for mentioning your earlier thread!