Cannot control librespot with the API

[Piano1234]

Plan

Premium

Country

Germany

Device

librespot, WebPlayer

Operating System

Windows 10

My Question or Issue

Currently I am working with this https://github.com/librespot-org/librespot-java software. I created a setup and it works fine.

I can start the playback from the WebPlayer on this device. I also tried to control the playback through the Spotify developer console. I used this endpoint: Start/Resume a User's Playback. The endpoint fail if I add a request body to this request. Without body paramters it is succesful. This is my error message:

{
  "error": {
    "status": 502,
    "message": "Bad gateway."
  }
}

I have no clue what the problem is. The librespot application cannot be the problem, because I can control it with the WebPlayer.

Has someone an idea what the problem is?

Thank you.