When defining app marketing developer site, some expected organizations are not available for JWT type.
For example, in this screenshot, users are expecting to see additional organizations.
The logged in user must be a System Administrator for the organization they expect to see. Being an administrator for the Marketing Cloud product/service is not adequate.
Have an existing System administrator for your org to add your Adobe ID as a System administrator. There may be a delay before the additional organization appears. Try logging out and back in, or clearing your browser cache if you don't see expected results.