Sometimes when you reinstall Kali, the installer shows this error executing grub install dummy failed
while installing grub and you have to skip this most important step to continue. The above commands are required if grub was not installed during the installation.
However if grub is present in EFI system partition but entry of kali is missing from boot menu options then you don't have to go through those commands. In hp PCs boot menu options, select
Boot from EFI
just below the Windows Boot Manager
.
Go to System>EFI>kali>grubx64.efi
Once kali boots open terminal and enter these commands
sudo grub-install /dev/sda
sudo update-grub
NOTE : For DELL users, there is no Boot from EFI option in your boot menu options but if you go to your UEFI settings you can add entry of bootloader from there.