on the system tray right click on the speaker, then choose " open sound settings", once in there choose our output device to whatever is should be, in this case it was DFX Speakers ( DFX Audio Enhancer) NOT REALTEK but if you are only using the onboard, it should say Realtek or whatever your defalut onboard is.
On the Input is should say Microphone (Realtek High Definiton)
scroll down and you will see " app volume and device preferences", click that make sure it is set to your defalut output device, is this case for me its DFX Audio Enhancer.
Once that is done. scroll down and look to the left for spotify, to the right is should say your default output in the first of the two boxes on the right, once you set that you should see spofify once again listed in your mixer settings on the system tray !