Just updated to Parallels 26 - now my virtual windows machine fails to start

This is a long established VM, which has worked for years through multiple Mac OS, Parallels and windows version upgrades.
I will attach a screen shot = "no operating system"
However, if I "ESC" from the "virtual" shell, I can select boot options and it will run, eg selecting: Windows Boot, EFI drive, etc.
I tried to change the boot order within the shell dialog, but it seems to only exist for the current session - ie save does NOT survive a shut-down restart of the vitual machine.
I does not appear that any options within Parallels can manage at the required level.