You are not allowed to accept this seek because you are already have 2 or more games against this opponent.To start another game against this player, please challenge them directly.

what is the reason for this?

Well, I can't answer with certainty but if you are already playing two games with someone it is unlikely they want another game with you when they placed the seek. The limitation prevents you from monopolizing all of a player's games.

If they wanted to play more games with you they would have directly challenged you instead of placing a seek.

yes, when you issue seeks by mobile, there is nothing to stop anyone accepting them all, say if you send 5 out. the new change stops the need to abort games against the same opponent, who may themselves be unaware of what they have done.

And there was no need to shout.