Files truncated and won't play after import

I’ve imported a group of m4a files into Audacity, and it looks good while importing, but when it’s finished the wave forms get all wonky and they don’t play. I’m very new to this work, and at 66 years old, not very tech savvy, so I hope someone can help lead me in the right direction. Thanks!
Screen Shot 2021-01-31 at 3.33.52 PM.png

The track is gray and silent because it is muted.
My guess is that the “Solo” button is pressed on another track, and that will cause all other tracks to be muted.
(see: https://manual.audacityteam.org/man/audio_tracks.html#panel)