More than 200 workers were dismissed after GRAM was placed into administration earlier in the year.
The mine ceased operating because an underground longwall panel was flooded with water.
The company representatives claimed no responsibility for inadequately managing the incident.
The workers were stood down without pay for two months in March, before the company eventually went into receivership.
Many of the workers have not been paid their full entitlements, with up to 60 employees owed amounts ranging from $1000 up to $50,000.
Meanwhile, all senior management staff at the company have been paid 100% of their entitlements, according to the Construction Forestry Mining and Energy Union.
A stalemate in the sale of the facility is holding up the payment of final monies owed to the workers.
CFMEU national secretary Michael O’Connor said a buyer had been found for the Cook Colliery but GRAM and its secured creditors the Bank of China, and the China Development Bank were at a stalemate, which is impacting the sale.
He called on the Chinese Ambassador to intervene, and seek urgent action from the Chinese government.
“It’s now been seven months since these workers were stood down without pay, facing an uncertain future,” O’Connor said.
“The workers and their families still haven’t been paid their full entitlements and have been subjected to extreme financial distress.
“Yet Cook Colliery senior management staff have been paid their entitlements in full.
“We need the Chinese government to break the deadlock on the sale of Cook Colliery, so these workers can finally get their just entitlements.”