There are calls to make the Covid-19 contact tracer app more inclusive, to get people using it again.
The number of daily scans on the app has plummeted from 2.5 million in September to around 500,000.
The Ministry of Health has confirmed older iPhone and Android models can't use the app's Bluetooth technology.
But Auckland University's Dr Andrew Chen says it can't be fixed through a simple software redesign.
He told Kate Hawkesby there'll always be the challenge of ensuring people have access to the appropriate devices.
"If people find they can't use all the app's features, they might not use it at all.
"Modelling suggests if the app is to be useful during a possible outbreak, we need 60 percent of people using it."