I think something happened to my Oculus speakers, but I'm not sure if there's something I could try, in case it's software related.
It all started while playing a game. When I went to adjust the rift a bit, while pulling from the left side, suddenly the left speaker muted, but went back to normal once I released the rift against my face again. Then I noticed that same thing happened to the right speaker if I pulled only the right side.
First I though it could be something about detecting if the rift is being used or not, to turn audio on/off, but it was weird that only happened on one side, and that I didn't notice it in all these months... I did a few more tries, pulling both sides (resulting in muting both speakers even if game was still visible on the lenses), or just one side or the other, being able to mute the individual speakers.
Suddenly, while still ingame, the right speaker muted. I tried adjusting the rift with no results.
I also tried switching speakers, but still right side is mute, so it's not speaker related, looks like sound isn't being sent to the right side speaker.
For now I'm playing using normal headphones, but it's a pain in the *** as it requires to constanly remove them before the rift everytime and adding more cables, not to mention configuring Windows sound from 5.1 to Headphones and back, so games don't sound weird.
Try removing the headphones and reinserting them. You can remove them with the small plastic screwdriver that comes with the kit. Sometimes they can get loose and just taking them out and blowing on the connection, and screwing them back in will help.