Multi Track Mixdown only silence

Hello,

Have a four track podcast recording. The sound information is there but:

1. Can't hear anything on playback

2. No sound information on the level meter while attempting playback

3. Export>Mulitrack Mixdown>Entire Session: only exports silence.

This was a student group recording in a University. When I came in to do a separate recording everything worked normally. So I can't figure out what these students might have changed to get to this circumstance.

• Imac Ventura OS
• PreSonus Studio 192 Audio Interface
• PreSonus Faderport 8 Control Surface.

Thanks for any advice

Robert N