"For our App players, the updated App is now available from the Apple App Store. For Android users, you'll be prompted to update your App."
Frustrated players were quick to question the timing of the upgrade which kicked in just after the draw last night.
"Sorry but what idiot decided it was a good idea to do a huge upgrade like this on lottery night?" one asked.
"Looking at the App it's not ready and obviously wasn't tested very well before it was signed off."
LottoNZ responded to messages on its Facebook page saying straight after the draw was the best time for the upgrade.
"Upgrading our system on draw night allows us to conduct the draw, complete all the ticket processing we do and not have tickets being bought or checked as we're trying to move to a new system.
"After a draw when everyone has bought a ticket and the draw is closed is the best time to do this. It also gives us time to make sure everything is working well before the next Lotto draw."
Others said the issue had put them off buying tickets online.
LottoNZ had warned players earlier in the week of the system upgrade.
Players were told the planned maintenance on Lotto's app and website meant they wouldn't be able to check instantly if they were a big – or small – winner.
The maintenance was expected to continue to an "unspecified time" on Sunday.
The numbers in last night's draw were 31, 3, 18, 34, 16, and 30. The Powerball was 8 and the Bonus Ball 17. The Strike numbers were 31, 3, 18 and 34.
Powerball was not struck so will roll over to Wednesday night, where the jackpot will be $12 million.
First Division was struck, with three lucky Lotto players each winning $333,333. The winning tickets were all sold on MyLotto to players from Auckland, Nelson and Canterbury.
Strike has also rolled over and will be $300,000 on Wednesday night.
