Volume button problem

Hi R4LX_L4RX​ 🙂

Maybe the button stuck somehow because of dirt or debris? Have you checked that? 

You can try this:

Rock the Button: Press the stuck button down firmly and gently rock it back and forth. Sometimes the plastic just catches slightly on the headset's casing. 

Clean the Gap: Dip a cotton swab in a small amount of isopropyl alcohol (rubbing alcohol), dab it to remove excess, and carefully wipe around the edges of the button while clicking it repeatedly. This breaks up sticky debris without damaging internal circuits. 

Use Compressed Air: After cleaning with alcohol, blow compressed air into the button crevices to clear loosened particles and dry the liquid.

If nothing helps, you might need a repair service like "Fix my Oculus" - if you are in the US - 

or google for vr headset repair service in your country.