Struggling to enable the PowerBI REST API to work, receiving "API is not accessible for application" as a response

Question

I followed this guide here: https://learn.microsoft.com/en-us/power-bi/developer/embedded/embed-service-principal#create-a-security-group-manually, but to sum up the steps I followed here:

1. Created an App with simple Report.ReadAll and Report.ReadWriteAll permissions to test access to PowerBI REST API with a sample workspace with a single report.
2. Created a simple Security Group with the App as a Service Principal.
3. Enabled content & access for Service Principals on the PowerBI workspace.
4. Added the Security Group & App as Admin for the PowerBI workspace as admins.

Following these steps, I just used a simple python notebook to work with the App ID, Tenant ID, & Secret. I used the MSAL library to generate the token, which works on the API on the website, but I am receiving Error 403: 'API is not Accessible for application'.