File Won't Play, Export is Empty Space

Hello! I am on a macOS Monterey version 12.5 with Audacity 3.1.3.

I just started using Audacity, and last week when I recorded my lecture I was able to save the file and playback to transcribe. I recorded the second lecture today, and everything was standard until I left my computer for a while. It won’t playback, but I was able to save the file. I see that there is audio through the visualization, but it won’t play.

I exported the file, but when I open the exported .mp3 there is no audio, just the 1:46:28 of empty space. Interestingly, I uploaded the empty mp3 to audacity, and it has the audio visualizations. I don’t know what’s gone wrong, and I’m worried I won’t be able to access the audio I recorded today.

Please help!