The English Football League has begun a formal investigation into Macclesfield Town's failure to pay their players.
Players at the League Two club went on strike last week over unpaid salaries.
Macclesfield have until 16:00 GMT on Wednesday to satisfy the EFL's request for information, with the threat of beginning disciplinary proceedings "if matters cannot be resolved".
In that eventuality, an independent disciplinary commission could impose financial or sporting sanctions.
It was reported on Monday that Macclesfield's players had been advised not to play or train because they were not insured.
However, according to BBC Radio Manchester, health insurance premiums have now been paid and players returned to training on Tuesday.
The EFL's statement said Macclesfield would be expelled from the Leasing.com Trophy if they failed to fulfil Wednesday's group fixture against Shrewsbury Town.
But that game is set to go ahead and will feature members of the first-team squad who were on strike for Sunday's FA Cup first-round defeat by non-league Kingstonian.
Macclesfield's team for that game featured six academy players and five loanees, and was played against the backdrop of supporter protest at the Moss Rose.
The EFL said it had already stepped in to fund salary payments at Macclesfield for July and September "through the use of solidarity and basic award payments".
Further difficulties understood to be caused by "challenges with the banking process" have delayed the payment of October wages, prompting the investigation.
Macclesfield have previously been taken to court by players over unpaid wages and in May, under then manager Sol Campbell, they considered boycotting the final match of last season for similar reasons.
There has been public interest from local businessman Joe Sealey in buying the club, amid the salary payment issues.
BBC Radio Manchester has contacted Macclesfield Town for comment.