User not registered in the Developer Dashboard 403 on /me endpoint

[david340804]

Plan

Premium

Country: USA

Device

Macbook Pro 2018

Operating System

MacOS 11.5.1

My Question or Issue

I've got my test app running for myself, but when I add another user they always get the 403 from the /me endpoint saying "User not registered in the Developer Dashboard" even though I added them by email over 30min ago. I've double checked the email and Name a half dozen times by now.

What else can I do to debug this?

Happy to share clientid or userid if those would help

Thanks