There are a few potential reasons why the Ubuntu live CD installer may fail to start.

Here are a few things you can try to troubleshoot the issue

To start the Ubuntu live CD installer, you will need to boot your computer from the live CD or USB stick.

If the installation media (e.g., the live CD or USB stick) is damaged or corrupted

and comparing it to the official checksum provided by Ubuntu.

heck the boot order in the BIOS/UEFI. The live CD installer may not start if the boot order is not set correctly in the BIOS or UEFI

(Unified Extensible Firmware Interface). To check the boot order

you will need to restart your computer and enter the BIOS or UEFI settings.

Look for a menu option that allows you to specify the boot order

To Get Complete Knowledge About It Then Check Link