FIFA has rejected Leicester City's application to register midfielder Adrien Silva after the club missed the deadline by 14 seconds. The Foxes agreed to sign the midfielder from Sporting Lisbon for £22m near the close of the summer transfer window on 31 August.
Silva's registration was not completed in time with football's governing body meaning the deal was not finalised.
Leicester is in the process of trying to appeal against the decision.
The Football Association has been in touch with FIFA and will look to help Leicester with its case.
A Leicester spokesman said: "We are working with Adrien and Sporting Clube de Portugal to overcome some issues relating to the player's registration and exploring all options to find a resolution."
Leicester still hopes to complete the deal but Sporting President Bruno de Carvalho added: "The transfer of Adrien is already completed. Hopefully, Leicester finds a solution for him."
France-born Silva, 28, is a product of Sporting's academy and has had loan spells at Maccabi Haifa and Academica.
He has earned 20 international caps and played during Portugal's run to winning Euro 2016.
Leicester also sold midfielder Danny Drinkwater to Chelsea for £35m in the final moments of the transfer window.
The English club had successfully sent through most of the paperwork for Adrien’s registration on time, bar one form, and because that form arrived late the whole process was rejected.
