Nottingham businessman Hardy had been expected to complete the purchase of the League Two club on Monday.
But the deal is being held up after it emerged the Haydn Green estate is owed a seven-figure sum.
Lawyers for Hardy and outgoing owner Ray Trew spent most of Monday trying to find a solution without success.
Hardy is chief executive of the Paragon group and owner of Nottinghamshire Golf and Country Club.
Notts have lost their past ten League Two matches and are 22nd in the table.
Alan Hardy's proposed takeover of Notts County is being delayed because of a dispute over who pays a £1m loan, reports BBC Radio Nottingham.