Doppler MP3 & FLAC Player funktioniert nicht

Doppler works as an offline music player and supports local music files.  Doppler supports a wide variety of different music file formats, including FLAC, MP3, WAV, AAC, M4A and many more.  To help keep your Library organised Doppler supports editing metadata for Songs and Albums — directly on your device and without the need for a computer.  Music and playlists are always stored local on your device, so you have your full Library whenever you need it — even offline.  Doppler's design adapts itself to match your music, and offers quick access to your now playing queue.  Import music and playlists to listen offline, and edit song and album artwork and info without syncing.  Music files are stored local on your device for offline playback.  Doppler supports Bluetooth and AirPlay 2 so you can listen in your Car or through AirPods, HomePod or any bluetooth enabled speaker.  Doppler is a beautifully designed FLAC player and MP3 player with support for many file formats.  Doppler even imports new files automatically to make sure your Library is always up to date.  Doppler also offers the option to find and download missing artwork.  Doppler works great for flights and the metro where you don't have WiFi.  Tap straight into a recently added album or use search to browse your music.  Doppler now also includes a CarPlay app.  Doppler is not able to import your songs or playlists from Apple Music.