I've had xbox for over a year now, and never seem to have had this problem.
Through my time ive been able to connect to people, join their parties, them join mine. and Sometimes when they couldnt i reseted my router and all was well again, however recently i cant seem to connect with an individual, we both have tried reseting, setting to default etc, both of our NATS are opens we both can join other parties but cant join a party one of us has created and therefore invited the other.
Besides this we both have the same internet provider : BT, which its connection status is stable and working, but we both live far away from each other
Know any idea on how to fix such thing?