Why isn't my hdmi audio working?

Hi, it's an Xbox One S

My monitor is an Acer and has speaker and a headphone jack and when I plug it into a TV it does work, I'm not too sure what os I'm using either

Hi Oliver! this is Manuela. I'm an Independent Advisor

I want to understand better your problem, for that please tell me:

What console are you using?

May I know if you're part of the insider program and you're using a preview or beta version of the Xbox OS?

When this started to happen?

What monitor do you have, and this monitor has built-in speakers?

Did you tried connecting the console to a TV and see how it goes?

And besides the procedures described in your post, did you tried something else?

I appreciate the extra information Oliver. If your monitor has an option to reset it to factory defaults please try that instead.

If maybe the issue persists and if you have a way to test the audio with a different device in your monitor please try that instead

Could be an issue with the monitor and not your Xbox

HDMI: HDMI Audio has stopped working on my Monitor.

OPTICAL AUDIO: Don't have any Optical Audio speaker systems.

Yes I understand that.

I think that there is more to it, I should have mentioned before. The setup is this. I'm connecting the Xbox to a cinema projector that only has a DVI connection not a HDMI connection. I'm also going through a box to extract the audio from the HDMI signal
to send it to the amps.

I'm going HDMI from the Xbox to the audio stripper box which then passes the PCM audio to the sound amps and outputs the video through HDMI which I have going into the projector using a HDMI to DVI cable.

The Xbox is displaying it's outputting DVI in the settings not HDMI. Is there a way to 'trick' the Xbox at all? I'm guessing there isn't. Also as it's stating it's outputting DVI I'm assuming it's not sending the audio too, which is why I'm not getting any
audio.