Leicester City are facing an anxious wait as they attempt to push through the £22m signing of Adrien Silva, five days after terms were agreed.
FIFA has refused to accept Leicester's documentation in support of the midfielder's registration.
Leicester agreed a deal with Sporting Lisbon on deadline day, but had to request a two-hour extension to complete the necessary paperwork.
Leicester's officials are working with Sporting to try to correct the registration papers, so that the transfer may yet be sanctioned by FIFA.