Help! API Connector throwing an error

I am trying to connect a Bubble app with a 3rd party tool (software called Creative Force). I have added the app on the 3rd party side, and tried to configure the API connector in Bubble. I get walked through the OAuth, enter my credentials, and get redirected back to my Bubble app. BUT, I get an error here and the API can’t complete authentication.

I think the issue is with my user id or user endpoint, but I don’t know.

The API documentation for the 3rd party tool is here:

The error is here:
The service connector apiconnector2-CNNx did not return an ID for this user. The user cannot be logged in. Please check your settings or reach out to the plugin author.

The API config is pictured: