Trade Me says system changes were to blame for a three-hour outage on Monday night.
The online auction website was down between 9pm to midnight and also on Sunday night.
Technicians were transferring core data bases from Auckland to Wellington on Saturday when the problems began.
Chief executive John MacDonald says auctions that were due to close on Monday night have been extended until midnight Tuesday.
He says technicians are looking at whether any traders were disadvantaged during bidding because of the outage.
