I had the same problem. While I was cleaning up my PC, I disabled a service that is needed for the beats audio software (IDT Service using msconfig). But, I don't believe that maybe your issue. Your issue maybe that the beats audio is not turned on. I noticed once I enabled the service that the beats audio needed, I still didnt have bass in the headphones. So I opened the beats audio control panel->listening experience and there it was a check box to turn on the beats audio. When I checked the box the bass immediately came in full throttle.
I hope this helps.