A source told ESPN FC last month that Hull agreed a fee with Wimbledon for Mannion, 18, amid interest from Liverpool and Stoke.
League One side Bury have been deducted three points for fielding an ineligible player.
Football fans have reacted angrily to a plan to allow Premier League clubs to field under-23 teams with up to four overage players in the EFL Trophy.
A local company has pulled its sponsorship of Chesterfield "in light of recent events."
Newcastle, relegated from the Premier League last season, head to Craven Cottage on Friday Aug. 5 to kick off the new EFL campaign.
Check out the full fixture list for the 2016-17 League One season.