In your BIOS, make sure you have the correct boot order set, as well as secure-boot and fast-boot
̶e̶n̶a̶b̶l̶e̶d̶ disabled. These things may have reverted to defaults after the BIOS update.
Edit: I had originally pointed to our buddy @cactux’s post here regarding boot-loader repair, but realised it was for systemd-boot, not Grub.