unable to accept people to corporation

tried to accept a player to my corporation and then this, i was able to decline, our rooster is far from full.



i was able to accept other players but this guy, he is still not in any other corporation. 


and now i declined hes invitation and then i spoke to him in chat, i invited him to corporation from chat and that seems to work.


Please ask them if they applied to more than 1 corp.

getting no answers from them.