Which image is installed on your SD card? Are you already using our new Buster Imager? You can find this information at the bottom of the debug info on the „Settings/Reboot“ page. If you are using an older image such as the Jessie or Wheezy image, please consider burning our latest Buster image to the SD card and rebuilding your system. If playback still does not work then, there is probably a hardware defect.