No Audio output from my Xbox

Dug out my original Xbox for something to do with kids in quarantine.

Ran a lens cleaner disk - worked fine, inc Audio.

Ordered a used copy of original Halo [got to home school the kids properly] and it played fine.

Went back to it next day and there was no audio output, not empty, not with the game, or DVD. Nothing. Tried changing TVs etc.

Did not change any settings,

Could it be the cable [looks fine, worked fine the day before]?

Could it be the unit itself?

Please help! Going crazy in quarantine!