I have no sound through display port on my monitor. It was ok on Win 8.1.
Don't want to believe that my monitor has problems or cable is bad. It was fine until I did upgrade to windows 10. After upgrade I made clean Win 10 install.
Using newest CCC and AMD drivers.
Win 10 x64 Pro, R9 290, LG 29UM67.
In CCC i can see that speaker icon on my monitor and when monitor is set as default sound device I can see those lights going up which indicates that sound is trying/going to that device.
My TV works with sound through HDMI.