[2022] How would two players with Restricted NAT [Red] be able to form groups?

So I purchased another copy for a friend to play with me. Unfortunately, despite attempts with my ISP at port forwarding, it's not a possibility with how it's set up for my location. I have a red nat type, yet no problems connecting to matches, staying in matches, or completing matches. However, whenever we try to join a group, I cannot join her group, and she cannot join when I invite either. It will consistently say "fail to join group, try again later" despite restarts all around. Is there any workaround or fix for this?