Matchmaking breaks every other match when on same network

When the game first came out, my roommate and I were able to play just fine. About 2 days after launch, it won't let either of us play together unless one of us is on a hotspot. ive searched for fixes since but nothing seems to work. I've tried port forwarding and enabling UPnP.  restarting PC's and routers, going wired vs wireless. Nothing works! just need some help, and maybe someone knows a fix?