Access Blocked when logging in ("Google's Policies")

When logging into Smarty on my mobile Facebook/Instagram app's browser, I receive an error:

"Access blocked: Authorization Error

You can't sign in from this screen because this app doesn't comply with Google's secure browsers policy. If this app has a website, you can open a web browser and try signing in from there."

Video Screen Recording: https://drive.google.com/file/d/1_j2QO0Q40FxcD76e4tKovAAEwpfeGXqW/view?usp=drive_link