403 Forbidden When using WebAPI

I’m trying to use the List Management web API ( BPCC List Management API v2.0 (getpostman.com)).
I get the authentication token without a problem.
But when I try to use it to, say, get a list of Campaigns ( configapi/v2/campaign/getAll/ ) – or any other call for that matter – I get a 403 Forbidden reply code.
Has anyone experienced this?
Or know how to fix it?

I know it’s probably a question of permission, but which one?

One of two solutions (choose any):
Add required privilege to the API user
1). “Manage all services and campaigns”
OR
2) “Manage assigned services and campaigns” and be assigned to the campaign as Administrator, Operator or Reviewer