This is almost always a computer issue. I have an HP as well, and it completely sucks. HP sucks. Period.
If you right click on your speaker icon on the computer, and open the 'Playback Devices' dialog, the computer should indicate the speakers available to use. I have connected my laptop to dozens of devices and the HP is about 50/50 in finding them and recognizing them. My Dell computer runs at 100% with the same devices, so I use my Dell or my iPhone to test HDMI w/Audio connections.
I went so far as to uninstall/reinstall all my HP audio drivers, and it improved things, but not by much.