Brentford have put a move for Antonio Nusa on hold and will reassess in the summer.
A club-record fee of £31.5million, including add-ons, had been agreed with Club Brugge, but the medical raised a number of concerns and the 18-year-old was sent back to Belgium.
Brentford sought more medical information from both Club Brugge and the Norwegian Football Federation.
The situation has made the Bees wary of parting with such a large amount of money, given there was already risk involved in the deal due to his age and inexperience at the top level, and will now return to the deal at the end of the season.
Nusa had been wanted by Chelsea, Tottenham and other top European clubs but the Bees' guarantee of regular first-team action attracted the teenager. The collapse of the January deal opens the door for other interested parties in the summer.
It has been a busy transfer window for Brentford, who have also signed Sergio Reguilon on loan from Spurs, midfielder Yunus Emre Konak from Sivasspor, and goalkeeper Hakon Valdimarsson from Elfsborg.
Valdimarsson’s arrival was going to see fourth-choice goalkeeper Ellery Balcombe allowed to leave on loan for more game time. However, the 24-year-old has recently had groin surgery to scupper an exit.
