I've just purchased a U3417W monitor but cannot get any sound from the built in speakers.

I have connected to a Dell XPS15 (windows 10) via DisplayPort (laptop mDP) and also via HDMI, sound does not work for either.

The default device in Windows is the "DELL U3417W" and when using the test play from Sound > Playback nothing can be heard. using the laptop builtin speakers does.

any ideas?