This problem keeps bugging me for many years since the day BT first introduced. I started using BT headsets for cell phone long before the first smartphone released, there are always connection problem, and the problem carry onto Linux. I used a BT speaker, it connected and tested ok on Debian with Cinnamon and Mate desktop, test in sound preference all fine, but nothing playback with sound, no matter it is a Youtube video or a local MP3 all muted, reboot doesn't fix that !?


Remember in the 'old days' all cellphone has a Infrared sensor built in for data communications, and I used IR to connect my PDA for internet no problem only slow, BT was designed to replace IR and can do much more, but simply a reliable connection is lacking how can I use that, file transfer also 50/50 chance worked on Linux that really sucks !

I've always had good luck with copper wire.

Bluetooth device should be set up as preferred device for music output (on top of the list), then your system will play through it when it is connected and fall back on the built-in audio when it is not.

You may need to configure the player you use or your sound (mixer?) settings. That is not changed by a reboot. Probably you only need to select the default device as it was explained in post #3.