If they have been invited by your fellowship, then the invited player has to accept. If the player who is not currently in your fellowships applies, then you can accept them.
I I am misunderstanding your problem, at least make sure that all parties involved reload their game to see if there is a status change.
Also, just to make sure, check your fellowship settings. I am not sure, but if you have auto-accept turned on, it may not show those checkmarks, as people will be added automatically when they apply.