FIFA has refused to accept Leicester’s documentation in support of Adrien Silva registration.
Leicester agreed a £22m deal for the 28-year-old Portugal international midfielder with Sporting Lisbon on deadline Day, but had to request a two-hour extension to complete the necessary paperwork.
Leicester lined up Adrien Silva after agreeing to sell Danny Drinkwater to Chelsea for £35m but could face the prospect of him not playing for them until January.
It is understood Leicester’s officials are working with the Portuguese club to try to correct the registration papers.
A Leicester City 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.”
Sporting said at the time in a statement: “Sporting Club de Portugal informs the market that we have reached an agreement with Leicester for the definitive transfer of the sporting and economic rights of the professional soccer player Adrien Silva. The registration of the same (player) is awaiting confirmation of FIFA.”
Silva is a product of Sporting’s academy and has had loan spells at Maccabi Haifa and Academica. He has earned 20 caps for Portugal, despite being born in France.
He is a Euro 2016 winner with Portugal and has scored 32 goals in 136 league appearances during his six years with Sporting.