Leicester City manager, Craig Shakespeare, said a deal was agreed for Adrien Silva and the club are still trying to finalise the transfer.
A £22million fee was agreed between Sporting Lisbon and the Foxes on transfer deadline day, with the former Premier League champions requesting an extension to complete the necessary paperwork.
FIFA state that they did not receive the paperwork in time, with reports suggesting it arrived 14 seconds late.
The Portuguese international seemed to be the replacement for Danny Drinkwater who moved to Chelsea on the last day of the window.
Leicester City will face Drinkwater's new side on Saturday, with Riyaid Mahrez remaining a City player despite much speculation about his future at the club.