No sound on tv when on hdmi but have sound when playing a dvd on hdmi

Nice to meet you, *****!
Let's check firstly the most important things:

1. Check if the cable has any problem.
2. Check if the monitor works properly. Make sure the monitor’s speaker volume is not turned down or muted.

Let me know when both items from the list are checked. 🙂

Got it.
And please also check if the output port works fine, Lydia.
If your PC has multiple HDMI output ports, try different ports and see if the problem resolves.
Please let me know once it's done.🙂

Noted.
Using other ports doesn't resolve the sound problem, am I tight?

Got it.
Let's check if the HDMI is set as the default device.
If the HDMI device is not set as the default device, you cannot hear the sound from HDMI output. Follow the steps below to set the HDMI device as Default Device:

1. Right-click on the sound volume icon in the lower right corner of Windows. A context menu will pop up.
2. Click Playback devices.

Let me know please, is everything clear for you, *****?🙂
If yes, I will tell you what to do next.

Noted.
Let's continue working according to the instructions, *****. Don't give up. 💪
We will handle it, step by step!

1. In the Playback tab, select Digital Output Device or HDMI option.

Click Set Default and click OK.
Then the HDMI sound output will be set as default.

Great!
You did it!
👏

I am so pleased to see your issue got resolved!🙂