'Youtube analytics API 403 error brand account

I've tried running the analytics/reporting APIs with my main account (using my local machine's terminal to run python scripts from the YT API Github), and came up with my brand accounts, I end up with an error 403 org_internal when trying to authorize via OAuth authentication flow.

I've also tried following the steps laid out here:

YouTube APIs - Access mutiple youtube channels (Brand Accounts) using Google Admin account

Once I get to step 6, I get the following error:

error 403 org_internal

and of course the request details are all fulfilled; there shouldn't be a problem with authorization (I'm not using a service account), scopes, etc...

I can use my main account for the API authorization.

2nd edit: Here is the OAuth query with the parameters I'm using: https://developers.google.com/youtube/analytics/reference/reports/query?apix_params=%7B%22dimensions%22%3A%22day%22%2C%22endDate%22%3A%222022-04-30%22%2C%22ids%22%3A%22channel%3D%3DMINE%22%2C%22metrics%22%3A%22estimatedMinutesWatched%2Cviews%2Clikes%2CsubscribersGained%22%2C%22sort%22%3A%22day%22%2C%22startDate%22%3A%222022-03-31%22%7D



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