Can't Invite Friend to MUT Squads ("Unable to invite player")

I am unable to invite my friend to play MUT Squads with me as it says "Unable to invite player. This player doesn't meet the requirement to join your current game mode."

I'm not sure what to do as we've been playing together for months and this issue just started yesterday. I've tried hard resetting, uninstalling the game, checking settings, etc. but nothing works. I haven't seen any other posts about this either.

He plays on PS5 and I am on the Xbox Series S.

Please help.