Can't record second track

Hi guys. I’m new to Audacity. Using Windows 10 on a Dell Inspiron 790 and Audacity 2.3.3
I am following the manual for recording multiple tracks, and get the first track down fine. Whether it is imported drum track from Acoustica Beatcraft, or my own guitar, the initial recording works fine. I can play it back, and hear myself playing along as well. The record meter even registers activity, as expected.
However, when I hit record to create the second track, I get nothing. I am set up to record straight to new mono track, so it’s not an append issue.
I hit record, a new mono track appears, the red triangle on the timeline sits at 0, (sorry I don’t know the technical term) but I can’t hear the previously recorded track, and my new track doesn’t record. I can hear myself playing, but nothing is recording. Overdub is checked, software playthrough is unchecked, as per the manual instructions.
The best way I can describe it is this, if this were an analog tape recorder, the pause button would be stuck. The lights are all on, the tape record heads are in contact with the tape, but nothing is rolling.
Please help!

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