for the key missing it is at least in my case RHEL8 due to UEHI or something like that and it can be disabled as outlined here:
https://docs.tenable.com/nnm/Content/DisableSecureBootforHighPerformanceMode.htm
it solved it but on the reboot it has a really strange password challange it asks for individual characters in the password that you set for the command... it asked for four or five different characters 5th character....etc repeated the loop several times... weird
never asked for the complete password.. it took me a bit to get it right..
good luck
