The journey was expected to take about 70 days, but on day three Donaldson hit a snag when his dry bag leaked and soaked his satellite phone.
The incident prompted Donaldson to head back to Australia and land at Port Macquarie, just south of his starting point.
“The dry bag leaked and the satphone is toast so I decided to call it before I hit the elevator east with no weather/current support,” he wrote on his website.
The 2000km journey has involved three years of planning and preparation.
Donaldson has had a kayak custom-built, with a compartment for sleeping, for the trip.
Australian kayaker Andrew McAulay died in 2007, within sight of the Fiordland coast, attempting to cross the Tasman.
His capsized kayak was found, but his body was not.