After uninstalling the old app and installing the new Hubitat Elevation app on my wife's Google Pixel 7, entering her email and password, it went to the select Hub screen as I have an older C-5 and a newer C-8 hub. It didn't actually allow me to choose between the two but the hub I use was shown. When I tap it, a pop-up states "Saving selected hub" with a spinning Hubitat logo. It never progresses. It's been spinning for 20-30 minutes. I've force closed the app. I've cleared cache. Cleared data. Uninstalled and reinstalled. I've done this multiple times. Always end up with a nice looking spinning logo.
Check the platform verison installed on C-8 hubitat. I was on version 2.3.9.164 and was having issues upgrading. I then restarted and upgraded (2.3.9.166), and I no longer have that issue. I hope this helps.
I finally got it to work by deleting their phones from the device list. As soon as I did that, when they click on the hub name, it prompts them to select an existing phone or add a new phone. Weird.