Unable to boot after Install

BIOS and hardware
Make sure that your BIOS doesn't has UEFI or Secure boot enabled, CSM and legacy boot must be enabled too

Make sure that the disk where you installed Elive is the first one found in the bios, so that the computer can boot from it first before to try another one.
Installation
The MBR is the configuration that makes your hard disk boot into the installed system, make sure that you have installed it in the correct device if it was not automatically detected.

You should have received a congratulations final message after the full installation proceeded correctly