The Scottish Football Association were unable to give the players the approval after an objection from the Ibrox club, who maintain that they have acted in breach of contractA lawyer representing seven former Rangers players hopes to see Fifa grant her clients international clearance in order for them to complete their moves to new clubs.
Kyle Lafferty was one of the players who opted not to join the Rangers newco after the old club was forced into liquidation when a proposed Company Voluntary Arrangement was rejected.
The Northern Ireland international has since joined Sion in Switzerland but could not make his debut against Grasshoppers on Sunday due to the inability of the Scottish Football Association (SFA) to issue international clearance after an objection from Rangers.
Steven Naismith's transfer to Everton similarly hangs in the balance, as does Steven Davis' move to Southampton.
Rangers, now owned by a consortium fronted by Sir Charles Green, believe the players have acted in breach of their contracts but PFA Scotland maintain they were free agents.
The matter will now be referred to Fifa, who have requested information from the SFA in order to make a decision.
"Following the refusal of the SFA to issue players registrations, the new clubs have all referred the matter to Fifa," lawyer Margaret Gribbon told the Press Association.
"Fifa have now written to the SFA in each case requesting reasons why the players' registrations were blocked.
"It remains entirely unclear the facts and matters upon which Rangers oldco and Rangers newco rely in order to support their position that the players acted in breach of contract.
"Presumably they have made their reasons known to the SFA and if so, these have not been shared with my law firm, Bridge Litigation, who represent the majority of the players.
"Fifa have given the SFA seven days to respond but it is hoped that given the straightforward nature of the request the SFA will be in a position to reply sooner.
"We remain confident that Fifa will grant ITC (International Transfer Clearance) enabling the players to continue playing football with their new clubs."