The ruined castle, which comes with 160 acres and a collection of largely derelict cottages, was sold last week but the property will return to auction once again.
Owner Gavin Farquhar said it was unclear why the sale didn’t complete but added : “We have had some pretty serious people interested.”
Mr Farquhar, who owns Ecclesgreig Estate at St Cyrus, south Aberdeenshire, said he had planned to open a tourism business at the castle.
But he is now no longer interested in pursuing the vision given Scottish Government policies on rates and empty building taxes, he said.
He said: “It was an interesting opportunity for us and we wanted to run a tourism venture on the estate, but we have zero interest in doing that now.”
Mr Farquhar bought Muness Castle for £65,000 in 2014, according to reports.
The property will be sold by Future Auctions, with the particulars stating that mineral rights to gold and copper reserves are included in the property following their discovery in a recent geological survey.
The purchase may also come with a barony title, according to the seller, although this has not been investigated by the auction house.
Historic Environment Scotland maintains Muness Castle, with the property described as a “splendid example” of tower house architecture.
It was originally built for Laurence Bruce of Cultmalindie – a deeply unpopular sheriff who is remembered for the oppression of the Shetland people. He is also portrayed as heroic in some legends.
He ordered his men to undertake acts of piracy on passing ships and changed the weights and measures system to boost his income from the Earldom. According to accounts, he fathered 24 illegitimate children on Shetland.
Bruce was half-brother of Robert Stewart, 1st Earl of Orkney, and from the late 1590s, Bruce had a series of disputes with his nephew, Robert’s son Patrick Stewart, 2nd Earl of Orkney.
The castle was set on fire by privateers from Dunkirk in 1627, though it was reoccupied afterwards. It was sold by the Bruce family in 1718 and fell into ruin.