Online Friendlies not working

I can not play with one specific friend. We're a group of six friends playing a custom tournament.

The problem is: We can play in every combination except me and Friend A. However we can play together Coop Seasons, Division Rivals, Squad Battles, UT friendlies and Clubs. And from Fifa 21 up to FC 25 no problems.

We did every suggestion there was. Resetet and updated the Rosters like 50 times. Looked at internet types, etc. Deleted of our EA friendlists. We just don't know what we should do now.