Check the phone for all its Bluetooth settings,
you should find settings for phone hands free settings, media player,
storage device settings, BT security, BT pairing, BT sharing.
Check media player settings and see that its active and set as needed.
May need to set storage as well, usually the settings allow it to act as a storage disk for data only, no streaming, or media player drive which will allow streaming and media playlists to be controlled by a media player-like MFT or other software on a PC, etc.