The Government's NZ Covid Tracer App has been failing to scan QR tracking posters or record manual diary entries in recent days, some iPhone users say.
One person - who did not want to be named - told the Herald they recently bought a new iPhone 11, but when they downloaded the NZ Covid Tracer App it would not scan QR posters at their local shops.
The app also wouldn't allow them to manually save a diary entry, instead flashing them a message to call the Government's Healthline.
When the person called Healthline, the operator said the support line had been receiving lots of calls from iPhone users with new and old models complaining the app wasn't working.
The operator said the troubles started about two days ago when Government programmers launched an update, the person said.
A Ministry of Health spokeswoman confirmed health teams recently became aware of an issue "preventing some iPhone users from saving new entries to their digital diary".
"The ministry released a patch to the app to notify affected users and prevent the issue from recurring in future," the spokeswoman said.
"Most affected users can resolve the issue by logging out and back into the app, or if that doesn't work, by restarting their iPhone."
If that didn't fix the issue, NZ Covid Tracer app users were asked to uninstall and reinstall the app, but they were likely to lose earlier diary entries.
"For these users - who are mainly people who have used the iCloud Backup service to transfer their information and settings to a new device or to restore a backup - it is not possible to recover any diary entries created prior to reinstallation," the spokeswoman said.
The woman who contacted the Herald confirmed that, saying she had been using the tracer app on her old iPhone, but those diary entries were not transferred to her new phone when she installed the tracer app.
Some Android users have also complained on Facebook about problems using the app.
One Facebook user wrote under a post on the Government's official Unite against Covid-19 page that their Android phone appeared too old to be compatible with the app.
"You can't download the contact tracer app if you don't have a newish phone. My Samsung is four years old and I rang the helpline - they told me that's why," the user wrote.
Other Facebook posters agreed, but others said they had even older Android phones and had no issues using the app.
Auckland is set to exit its level 3 Covid-19 restrictions on Monday morning and the Government has been pushing for more people to download and use the app.
Earlier this week, it reported there were now more than 1,800,000 people registered to use it.
Health Minister Chris Hipkins said QR codes - which when scanned by the app record the location as a way to track the user if they potentially come in contact with a Covid-19 case - will be mandatory on buses, trains, taxis, ferries and rideshare vehicles from Friday next week.
Private vehicles will be exempt. Drivers will not be asked to ensure passengers scan the QR codes.
He said it would provide an extra layer of assurance and speed for contact tracing.
He said it was faster to get in touch with people if they used the Covid Tracer app, which was also more useful than Hop or Snapper cards.