EAC Error Code: 20006 Upon Startup

So when my brother accesses MCC - whether it’s running on administrator or messing around with the EAC services - the EAC loads up like normal you would think, then gives him an error message with that error code (20006).

We both diligently tried to find a solution to this problem but we ended up with no luck in the end. The only way he is able to play is if he uses the (Mods and Limited Services) version of MCC; and only then he is limited to campaign and firefight; both of which are capable within co-op and solo. Due to this, he can’t play in multiplayer or firefight multiplayer.

Got any solutions?