Mobile App and Nabu Casa

I have had the mobile app (Android) working perfectly for some time now on my local network but I have decided to try Nabu Casa.

But, after several reinstalls and reconfigures of the app I still cannot get it to work.

I have the following configuration…

image

…but the app starts, shows the HA logo and ‘Loading Data’ before going to a white screen with a plain header bar with a non functional hamburger menu but the wheel spins for a few seconds before the app crashes.

This happens both on WiFi and off it.

The only way to get the app to start again is to clear the cache and data and start again from the beginning.

What do I have wrong?
Is it the app?
Is it Nabu Casa?
Is it something else?