Boot Menu Problem

I installed Kubuntu on my HP All in one Desktop Pavilion 23 four years ago. I have kept it updated, but would like to try another distro. I wanted to try Zorin, but for some reason I can only boot into Ubuntu. When I see the boot up menu, I can navigate to the DVD drive. However when I hit enter, nothing happens. I tried also with a USB and ran into the same problem. Does anyone have any idea what is causing this? Not sure if I should have asked here, or in the Ubuntu specific thread.

I am a senior citizen.

many of us would like to see 50 again [but it will never happen]

I can navigate to the DVD drive. However when I hit enter, nothing happens
did you remember to burn the DVD as a bootable image?
did you check the SHA sum?
if yes to both above, try again with a clean DVD-r disc and burn at the slowest speed 2x or 3x

Thanks for the reply. OK I wondered if this could be the problem. Also the actual download took eight minutes. That seemed rather long to me, but I live in Europe and download time can take awhile where I live in Germany. However when I look at the contents of the burned image, it all seems to be there. I used Brasero to burn it. Simply burned the image. I saw no other option. I am not sure what you mean by the SHA sum. Like I said I am not all that computer savvy, although I have used Linux in one version or another ( KDE, Suse, Mint and now Ubuntu or Kubuntu) for over ten years. A friend who at the time worked for IBM suggested it, when my version of windows expired. I can follow simple instructions, but I honestly have no knowledge of computer programming ( perhaps not the right term ). I have great difficulty using the Terminal Command. FYI I am 75, well over 50 I am attaching a screenshot of the Zorin DVD Disk. Re the USB stick, my computer did not even show it in the boot menu. I used balena Etcher to flash that, as per Zorin install instructions. When that didn't work, I tried burning it to DVD.

OH yes regarding the USB stick. It did show as Zorin using Dolphin to access removable drives.

Your main mirror for zorin is https://ftp.halifax.rwth-aachen.de/zorinos/

however, you may find Thessaloniki university a good alternative https://fosszone.csd.auth.gr/zorinos/

Thanks, I am in the process of trying to burn the image at a slower speed. Will try that and if it doesn't work will try to download Zorin once again.

Thank you very much Brickwizard! I re-downloaded Zorin OS from the Aachen mirror, and used balena Etcher to flash it to the USB drive. This time when I booted, it showed the USB drive, and I was able to boot from it. Thanks much! I think I am going to install Zorin as soon as I save tons of files that I have here, onto a new external drive.