I just had the blank screen when using the trailering app happento me.
This was the 1st time I actually needed to use it on my new to me 2020 Trail Boss.
I plugged my 4 pin flat trailer plug and the screen was blank, but everything else would work just the trailering app was blank. I googled it on the internet, and found others having the same issue, and the fix was to reset the infotainment system to factory settings?? When I went back to my truck it started working again and I never had to do the factory reset.
I re-hitched to my trailer and the app worked great, a very helpful app, and I hope this doesn't happen too often.