The National Australia Bank is struggling to stabilise its Transact payments gateway after consistent log-in issues, timeouts and transaction errors over the past month.
The Transact service is a customised version of Australia Post's SecurePay and is used by retailers to accept online payments securely.
After several weeks of intermittent issues, AusPost performed an upgrade to SecurePay on Tuesday to improve its stability, but the upgrade had unintended effects to NAB's Transact platform, rendering it unavailable at times.
"We unreservedly apologise to those customers who could not access the system," Australia Post said in a statement.
NAB placed the Transact system in "hypercare" on Tuesday, but today informed customers the platform was still experiencing intermittent errors.
Some merchant customers attempting to process credit card transactions through their websites are receiving error codes, timeouts and "bad gateway" alerts, NAB said.
Other customers submitting payments for batch processing were receiving a "suspended status" notice, and were requested to resubmit the file.
Customers may also continue to experience issues accessing the portal and with the reporting function, NAB advised.
It said the root cause of the issue is still under investigation, and promised to update customers again at 6pm today. iTnews has contacted NAB for further detail.
"Our team are continuing to implement key improvements involving the web payment servers used for the NAB Transact Platform," the bank advised.
"NAB Transact remains in hypercare, and additional testing and monitoring is taking place."
In an open letter to Transact customers earlier this week, NAB executives Mark Adams and John Murphy apologised for the "frustrating" experience.
"We want to ... assure you that the team at NAB is doing everything we can to fix this. Resolving this issue is an absolute priority for us," they wrote.
Jeans West, online lingerie retailer Zodee and federal government agency IP Australia are among numerous customers affected.
"We are just as frustrated as you are about this but NAB have assured us that they are working to resolve this issue ASAP," Jeans West told customers.
"In the interim, you can still purchase your favourite must-haves using PayPal."
IP Australia was forced to set up an emergency fax line to continue processing customer payments until the system and its own eServices portal could be stabilised.
"National Australia Bank (NAB) continues to experience ongoing technical issues with its payment gateway and is unable to provide a timeframe for resolution," it advised customers today.
"Unfortunately we are unable to invoke our eServices portal until these issues are resolved."
It said it would offer reduced fees to all submissions for IP right services during the period of instability.