DiscordPHP: Can't play a file with VoiceClient::playFile()

Environment

• PHP Version:
  • 8.0.9
• DiscordPHP Versions:
  • dev-develop
• Ubuntu 21.04
• FFmpeg

Describe the bug The bot joins my voice channel but plays no sound. There is no error and it looks like it can find the mp3 file. Also tried a .wav file.

Code

$discord->joinVoiceChannel($voiceChannel, false, false)->done(function(VoiceClient $voiceClient){
    $voiceClient->playFile("dt.mp3")->otherwise(function($e){ echo "ERROR: ".$e->getMessage(); });
});

Expected behavior Join a voice channel and play a sound.