Nevermind! I got it to work!
Uninstall the Duo app from the phone
Reopen the newly installed Duo app from the phone and allow push notification
Open the applewatch Duo app and it works!
I’m having the same exact issues. I upgraded my phone to 12 Pro Max and all of sudden, the Apple Watch app says no account found. I tried all of the methods suggested on here but nothing seems to work… I’m about ready to give up and remove the app ...