MLS help: Unable to register player

Hi all,

Could someone who's played the MLS before explain to my why I am unable to register Chris Eagles? (see attachment)

He is suck in 'Out' status and have no idea why, due to this being my first time in the MLS.

Thanks for any help.

Note: Ive already tried clearing the squad, in case it had something to do with min / max rules or salary cap.
He is currently injured (Orange) however my understand is all injured players are automatically registered anyway.

thanks for any help.