You are brilliant. Of course I could do the synch with a bare bones phone because the ST app wasn’t on it! Once I restored my phone, I tested again and it failed again. So then I looked at your solution. In my case it’s App Settings->SmartThings->Set as default-> turn of the “Open supported links” and bingo, I am back in business. Too bad I didn’t wait for you to point out this tip. I wasted a lot of time backing up and restoring my phone.
The only benefit of the reset was it seemed to have cleared up a problem I was also having with the Samsung account. When it goes to the Samsung log in page, if I chose “Sign in with Galaxy device” it would fail saying my Samsung account needed to be updated. But the Play Store said I was already on the current version. So I would have to choose “Sign in with your account ID”. That problem has now disappeared.
So thanks again. As always, you have been very helpful!!