This issue was suprisingly fixed by changing the order in which plugins were added.

In main.dart

from

Amplify.addPlugins([authPlugin, dataStorePlugin, apiPlugin]);

To

Amplify.addPlugins([dataStorePlugin, authPlugin, apiPlugin]);

And the following commands were required for me

flutter clean

flutter pub get

flutter run -d iPhone

Don't know why this was never referenced or needed by Amplify as authPlugin has no requirements for dataStore