Couldn't Sign You In

I am trying to setup OAuth2 authentication for Google Photos API requests.
I have set this up in Google Developers API & Services.
When I complete the form in Postman and click Request Token, I get ‘Couldn’t Sign You In’.

Can anyone help me figure out what’s going on?

I was able to login with a work account that is a paid account and get a token. However, when I make the request I get an empty JSON response of {} - there should be data there. I’m not sure if that’s because the work account cannot access my personal account’s API setup or if there’s a problem with the request. Either way, I don’t want to be using that work account at all - I only tried it to see if I could login at all to get a token.