|I have no idea why it was marked as resolved either and can't change it.|
So you've verified it's not a firewall at either end of the connection? I ask because the fact that it only happens between you two, and not you and others, indicates the issue is limited to one or the other of you.
Both of you need to check your router's firewall rules and port forewards, also check the firewalls running on your PC's.
It matters not how straight the gate,
How charged with punishments the scroll,
I am the master of my fate;
I am the captain of my soul.