Even H4 Headphones - Right hand side headphone stopped working

I have a pair of Even H4 bluetooth headphones. It seems the manufacturer has gone out of business though their website is still up.

The right headphone no longer produces sound but the left headphone works well.

Is there, perhaps, a reset action that I can take to try and make the right headphone work again?

If not, is there a guide for disassembling the right headphone in order to repair it?