Welcome to the forum!
Several things you can try out that could isolate the problem. Please give them a try and report back and I can try to help further based on what you find. Also, if none of these help could you please go in to a bit more detail about what's not working (i.e. black screen, tv says no signal, picture quality not what you expect, etc.)
- Use the same HDMI cable and PC on a different tv. If it works you know the cable isn't bad. You should do this first anyways to verify your PC is properly outputting video.
- Do you know for certain the HDMI port works on the tv? Is the DVD player plugged into one input on the tv in question? If so, take the HDMI cable for the DVD player out of the TV and try to connect your PC to the HDMI port that the DVD player was connected to. If that works then the port may be bad. Try to connect the DVD player to the HDMI port you were previously trying to connect the PC to.
- Try a different HDMI cable
I can continue to add ideas but let's start here. Good luck!