Two different people came to me with this problem this week. The Recording Level goes to zero without warning or user interaction.
In one case, the RL slider went to zero, but Audacity continued to record at the user’s normal level, so it may be a UI issue. The RL setting continued to change to zero every time the user reset it, as soon as they hit Record. User tried restarting Audacity, restarting the computer, and reinstalling Audacity, all without change in behavior.
In the other case, the user exited Audacity and restarted it, and the indicated RL returned to normal on its own.
In both cases, the users reported that 3.3.3 had been running successfully on Big Sur prior to the onset of this symptom within the last 3 days (it’s currently Sep 03 2023).