Surface Pro No audio to external monitor

Actually, I found going into Device Manager and disabling and then re-enabling the "Intel(R) Display Audio" driver solved the problem for me.

1. Right click on the start button, and select "Device Manager."
2. Look for "Sound, video, and game controllers," and expand its section.
3. Right click on "Intel(R) Display Audio," and select "Disable."
4. Then right click it again, this time selecting "Enable."

This was done on the anniversary update with the latest drivers. You may have to try unplugging and then plugging back in the HDMI cable between steps 3 and 4.

This one was weird, but I was having the same problem about 5 minutes ago.  Try going to  control panel > sound > manage audio devices > click on your tv device and edit properties.  Go to advanced then change the default format around a few times and test.  The first two I tried played no sound.  The third one I tried said that the device was in use by another application and asked if I wanted to stop it.  I clicked yes and now I have sound.

Good Luck!

ok I did what he said here:

I was connecting to my Onkyo receiver Aux input

Went to control panel -> sound. 

Properties

Advanced Tab

Clicked a bunch of different quality levels... nothing seemed to change.

Picked 16bit, 96000 hz.   It said "device in use" I clicked yes.

No sound, BUT I noticed that on my Onkyo the display started changing when I played the test sound...  turned out the test sound was too short, the receiver couldn't "Detect" the right format and switch to it fast enough... I got one tiny "peep" at the very end that clued me in...

So I loaded a video file with a lot of audio, and wham it detected (after about 1-2sec) and now I get audio.

I'm pretty sure I had to do the thing on the advanced tab before it started "working" because I didn't hear any "peeps" before that and I tried on other TV's (directly) and it didn't work, but in this case the delay on switching/auto detecting made the problem even more frustrating to detect (that I had fixed it!) when the test sound was too short!  (maybe that's why some people on this thread said it works on the TV, but not when using a receiver!  Try a long clip of something in the background.)

Thanks!