way to restore "bootx64.efi"

[Henry <nbsd4ever%gmail.com@localhost>]

In my attempt to update the bios on hp notebook 15au123cl, it seems I
rendered the machine unbootable.
The actual message when attempting to boot from an efi file is
"Selected boot image did not Authenticate."  If I try to boot directly
from the ssd, the error message is something like "Selected disk
failed."

Praying there is some way to recover.  TIA

Henry