The VM's boot settings are located in the VM's non-volatile random-access memory and this isn't a file that is backed up. Therefore if you restore a VM with changed boot settings, this non-default setting will not be available and you need to reconfigure the BIOS.

Upon boot at first you will be greeted with this screen:

In order to reconfigure the BIOS, you can use the following instructions:

  1. Ensure you have administrator or super user (root) access to the VM.

  2. If you want to force the VM to boot directly to the BIOS screen (if it's not); in vSphere Client, select [Force EFI Setup]. In vSphere Web Client, select [The next time the virtual machine boots, force entry into the BIOS setup screen]. Then simply power on the VM

  3. Next, select [Boot Maintenance Manager], then [Configure boot options]

  4. Then simply configure the boot options as they were previously, for instance if your VM had a grub.efi boot loader, click [Add boot option]. Then simply browse to the grub.efi by selecting the boot drive, [EFI], [VM OS] and grub.efi. Then commit the changes.

  5. Then select [Configure boot options] and [Change boot order] in order to choose to set it back to the way it originally was. Again, for instance if the VM was configured via the grub.efi boot loader, you need to make sure that it's the first entry in the list.

  6. Once you're done, simply exit the boot manager and select [Continue]. The VM should now boot up just fine.