Homey Energy Dongle Authorization for Third-Party Apps

I am trying to integrate my Homey Energy Dongle with a third-party app.
I registered an account on the Homey Developer Platform and authorized users who own the Homey Energy Dongle under my developer account. I am using the authorized user’s token to retrieve their devices.
However, while I can successfully obtain the access token via the https://api.athom.com/oauth2/token endpoint, the https://api.athom.com/user/me endpoint fails to return any device information for the current user—specifically, it returns an empty list: "homeys": []. Could you please help me understand why this is happening?

Do you use Homey Cloud? In that case, you can’t test custom API integrations, you need to contact Athom to get approved via the “Request Limit Increase” link