I can only hear out of one of my earphones?

It may be that you have stereo earphones that work with other stereo equipment -your old earphones the same.

But the equipment you use - you do not say what it is - sends out only one channel - mono output - your earphones are fine.

Your equipment might have a failing second channel but it may also be working as it should - you do not say if it ever gave stereo two-channel sound. Your 'phones certainly do.

What does the manual say?

Good Luck...
February 2016