Hi, my problem wasn't that Android auto didn't work. My Android phone connected and worked fine. My issue was that the connection error message would come up every 5 seconds stating that the connection was unstable.
Hello, I had this same issue with my F150 Sync 4 and a Samsung Galaxy S21 Ultra.
The issue seemed to be with the Android lock screen permissions. I solved the issue by:
Go to Smart Lock on your Samsung phone and add your Sync 4 car connection to Trusted Devices. That warning message has not come...