Matchmaking - Only works for my account?

I’ve had no major issues finding games since the most recent patch.

However, my girlfriend tried to play Matchmaking today and was unable to get into a single match.

We’re on the same console and everything. :\

Well, now it’s not working for me either.

Nat is open. Ports are forwarded for the Xbox One. Internet isn’t having any issues.

Literally just MCC…