Solved All bluetooth headphones are being set as headsets

If only the headset mode is working and you cannot make the headphones connect, verify you have the AVCTP service enabled.

JohnLeitch said:

If only the headset mode is working and you cannot make the headphones connect, verify you have the AVCTP service enabled.

Click to expand...

I signed up and created an account just to post on this old thread, that this is the solution.
The issue for me was exactly that the AVCTP service was not being started up on boot.

I tried 3 different USB bluetooth dongles, all of which paired 2 different sets of headphones onto other PCs running Windows 10 with no issues.
I cleared the Bluetooth settings & devices multiple times, did all the normal system health scans and checks, but no matter what i tried, all headphones in this one PC would only connect in "headset" mode, and nothing else.

Manually started the AVCTP service, and the headphones immediately transitioned from "connected voice" to "connected voice, music"

So hopefully its not too late for OP to discover this instead of replacing their whole motherboard!!