Like everyone else, was having issues setting up downloads for cards with Synchrony Bank - something I was doing as part of starting to manage my MIL's finances. What frustrated me is that I had no issues with my own accounts.
Read several posts about it being a URL issue. I went through each option that presented when you typed in SYN in the search and found that the URL shown, Synchrony Financial Mastercard, took you to the same login page as my cards - so I tried that but still got an error when using my MIL's credentials; yet when I used my credentials, it was successful.
So i changed my MIL's password to the same password as my own and it WORKED!!!!
So I am thinking that my MIL's password was just too complicated, even though it was going to the right URL.
[Edited-Readability]