I had the same issue on both my dell and my surface pro 7: they would connect and pair with the headphones but not recognize them as audio devices.
**Method 1 listed above worked on both laptops.**
I restarted all the Bluetooth services.
And then removed the headphones and re-paired them.
When pairing again, the headphones correctly connected as audio devices.
I'm not sure why this worked since all those services were running anyway but it triggered something.
Note: not all the Bluetooth services listed in method 1 were on my laptops: the dell only had 1 bluetooth service listed and the surface pro 7 had three listed. They were also named differently, but restarting them worked.
Both laptops are up to date Windows 10.