Paris Saint-Germain have failed in an appeal to register the loan signing of Hakim Ziyech as Chelsea sent over the wrong paperwork to complete the deal three times.
The Morocco international spent deadline day in the French capital as he looked to secure an exit from Stamford Bridge.
Everything seemed to be going smoothly and there was optimism a deal would be completed prior to Tuesday's deadline.
However, the move has collapsed as the signing was not registered in time.
Reports in France that Chelsea were so fixated on signing Enzo Fernandez from Benfica for a British record deal that they accidentally forwarded the wrong paperwork to PSG on three occasions, preventing the Ligue 1 giants from completing the formalities required.
PSG and Chelsea appealed the decision to the French footballing authorities but this was rejected on Wednesday morning.
Ziyech had plenty of other suitors throughout the January window, including Newcastle United, Everton and Milan. Former side Ajax have long been linked with a reunion, too.
But he will now remain at Chelsea until the summer at least.