Someone know... ?

Hello, i'm a bit newbie in this game and i have a question about "auction player"
Attachment 10585

I "won" this auction at the last momment.
As allways, i fired a "less-quality" player, but... I can not add the player i won into my team.
Someone can help me ?

Thanks !

could be that you already have 22 players. you have to have an open spot available to sign more players.