Android app: Handshake Failed on login

I am just getting started with BitWarden and have installed my own Bitwarden RS server which seems to be running fine.

I have successfully connected from multiple Android phones and browser plugins where it works perfectly, but when I try to connect using the Android app on my wife’s tablet I get an error message “Handhake failed” when I try to log in.

I have configured the server URL in the settings. To make sure I didn’t make a mistake in the URL I copied it to a browser using copy/paste and in the browser it works fine and I can log in.

Also, when I try using the app there is no entry in the Bitwarden server logs at all so it looks like the app is somehow failing completely to contact the server.

In case it is helpful, the tablet is a Samsung running android 7.0 and the app version is 2.2.8. Any help/guidance would be much appreciated.