Kettering Town have been placed under a transfer embargo after failing to pay their players' wages in full, BBC Radio Northampton understands.
The restriction came into force on Monday, meaning three signings completed this week are null and void.
MK Dons striker Charlie Collins and Peterborough pair Peter Grant and Michael Richens will not join the club.
However the signing of ex-Aston Villa defender Ellis Deeney does stand, as it was completed last week.
Youngsters Collins, Grant and Richens were advertised as having joined the Poppies by their parent clubs, but the deals have not been ratified by the Football Conference.
Boss Mark Stimson lost five members of his squad prior to Thursday's loan deadline.
Departing the club on loan, with permanent moves agreed for January, were Aman Verma, Marcus Kelly and Adam Cunnington. Moses Ashikodi has joined York City on loan, with a view to a move early next year. Jean-Paul Marna was loaned to Corby Town until January.
A series of injuries means the Poppies manager will have to turn to his youth team to field a side against Grimsby on Saturday.
The departures come after club chairman Imraan Ladak placed every member of his squad on the transfer list, for football and financial reasons.