also make sure there is a timeout on the grub boot menu GRUB_TIMEOUT=5
save and then run update-grub
update-grub
Generating grub configuration file ...
Found linux image: /boot/vmlinuz-5.13.19-2-pve
Found initrd image: /boot/initrd.img-5.13.19-2-pve
Found memtest86+ image: /boot/memtest86+.bin
Found memtest86+ multiboot image: /boot/memtest86+_multiboot.bin
Adding boot menu entry for EFI firmware configuration
done