Good evening
When you have 32 players in your squad, you can't trade players. Since I've been on the game it's always been like this, but I think it's a bug.
Indeed, the maximum number of players allowed is 32 players, but this should not prevent you from making a trade, because numerically, there are still 32 players after the trade.
@aymeric45

You are right....

But yes it's clear 😂