Avantis4U is not connecting to my iPhone 12 Pro. When connected to the network, the console shows as available but then shows an error message and will not Connect. Also under settings on the phone the app does not show up on the app list. I have this working on my iPad but no luck on the phone.
My only suggestion would be to make sure the app and the console are running the same version. If you had this all working with the console and iPad previously and only recently tried to add the app to your phone, it could be that A&H has released a firmware for the console since you got it working on the iPad. The newly downloaded app on your phone expects to see the latest console firmware version, but the console is actually on an older firmware version.
Not sure if that is the problem or not, but it is easy enough to check.