Hey there. I have been looking over this issue that I have to no solution. Here is how my PC is set up:
Headphones are connected through the front panel (so is the mic) and the speakers are connected directly to the motherboard (front, rear and sub, since I have a 5.1 setup).
Everything plays normally through the speakers except Spotify. Spotify plays through the headphones when I choose the headphones as a default output devide from windows. I can not play any song another way.
When I try to play music though the speakers, I get a message : Spotify can't play this song right now. If you have the file on your computer you can import it.
I have tried the following solutions to no avail from searching online: