Auckland Transport is asking customers to reset their auto top-up settings on their travel card, amid more technical difficulties.

Last week a ransomware attack took out the city's AT HOP system, disrupting commutes for passengers. It took multiple days to be restored.

On Tuesday, some commuters received an 'insufficient funds' notification when they tried to tag onto public transport.

The agency said the issues were a result of last week's attack. It said the system was experiencing a few residual issues that it hoped would be resolved in the next few days.

Customers will need to update their auto top-up and then tag onto one of AT's services to fix the issue.

AT said no money had been deducted from customers' credit or debit cards during failed attempts to tag on.

Executive General Manager Public Transport Services Stacey van der Putten said the problem was an unforeseen part of the restoration.

"We haven't charged customers for trips they have not taken, but customers may find they have a negative balance for trips they have taken in the past week that have not been covered by an auto top-up," she said.

"We apologise to customers for this inconvenience and thank them for their patience as we work through fully restoring our system."

AT said drivers and staff have been told customers affected by the problem can continue to travel until the end of the day Wednesday on buses, trains and ferries.

What to do

AT HOP cards can be topped up in person at a customer service centre, ticket and top-up machines, or AT HOP retailers.

Customers can also top-up online, but this will take longer to process.

After this, customers should re-enable their AT HOP auto top-up online.