Unable to join game session. Players not on latest game version. Happened in Aug

Since the patch this week I am not able to play other members in my league - it states one or more of us is not on the latest version of the game - I am able to play online h2h ranked matches but cant connect in a CFM - this started right after the patch this week - please advise how to fix this ASAP - I read online you have to rebuy the game and I dont want to pay twice.