Can you hear on both sides of the headphones if the headphones are plugged into another audio source?
Do other headphones or speakers work correctly when plugged in?
Another thing you can do is to plug in the headphones into a known working audio source and, while listening, gently wiggle, bend, and twist the headphone cords. Especiallly close to each earphone and the plug. See if you can make the right side work - even if momentarily. Could be a break in the wire.
The goal is to determine if the problem is the headphones are not working (right side) or if the problem is related to the AUX port.