Unable to use U-verse on Iphone or Kindle, getting error "U-verse mobile service is temporarily unavailable"

I am getting this error "U-verse mobile service is temporarily unavailable".  This has worked for years.  I am using the Uverse app on an Iphone 12 and a Kindle Fire, get the same error.  Obviously I tried rebooting both, and uninstalling-reinstalling the app on both.  I tried changing my ATT.com password, also I verified my email through ATT.COM.  ATT.COM works fine on my Windows 10 computer.  I also tried disabling WIFI on the Iphone forcing it to use cellular data and the same thing happens.  I called Tech Support and we went through all of this stuff.  he said the app support is through a third party and call back during business hours.  Why is this so hard?  This is obviously an ATT issue, seems like I have this same problem once or twice a year, not to mention that when the app works it locks up and cuts in and out.  If I find the magic answer I will post it.