Chelsea winger Hakim Ziyech's proposed loan move to Paris St-Germain has been blocked by France's governing body, the LFP.
But PSG sources were critical of Chelsea's conduct, claiming required paperwork was not submitted on time.
Ziyech was in Paris expecting a deal to be confirmed, but the registration was not completed and so he will return to Chelsea for the rest of the season.
BBC Sport understands the player contacted Chelsea owner Todd Boehly directly in an effort to resolve the matter, but his pleas were ultimately unsuccessful.
The issues are thought to have involved legal agreements between the two clubs, which were in order and just needed signing.