I’m a new user. Audacity 3.7.1, Windows 11. Not doing anything fancy, just trying to split an mp3. Can 't hear any sound whatever. I have checked the audio settings in preferences. Very annoying. Any help would be much appreciated.
You’ve selected the correct playback device?
The playback-volume slider is “hidden” behind the playback meters, is it turned-up (to the right)?
Do you see a waveform? Do you see activity on the meters when you try to play?
A note about MP3 - As you may know, MP3 is lossy compression. Information is thrown-away to make a smaller file. (It tries to throw-away details you can’t hear.)
When you open a compressed file in Audacity (or any regular audio editor) it gets decompressed. If you re-export as MP3 you are going through another generation of lossy compression and some “damage” accumulates. You may not hear any quality loss but ideally you should compress ONCE if you want MP3, or otherwise try to minimize the generations of re-compression.
There is a special-purpose editor called mp3DirectCut that can do some limited editing without decompressing. (Don’t ask me for help with it… I’ve only used it a couple of times. 
)
Thanks for the info re mp3 quality loss every time a project is saved. Good to know about MyDirectCut.
As for the volume slider, it’s very hard to see. Thanks for the tip. That may be my issue. I’ĺl take a closer look.