The English Football League have rejected Oli McBurnie's loan move to Barnsley.
The Swansea striker had moved to the Championship club on deadline day, but the league has ruled that the administration part of the transfer was not properly completed.
Barnsley chief executive Gauthier Ganaye said: "We are naturally extremely disappointed, but we respect the English Football League's decision and thank them for their communication throughout the process.
"Oli showed a huge desire to come and play for Barnsley which can only be admired and ultimately this decision will have the most impact on him.
"We are disappointed, but understand that although the player was identified as a significant target over two months ago, we were unable to try and effect the registration until the last moments of deadline day.
"We wish Oli nothing but the best of luck back at Swansea City in their Premier League campaign."