Failure to boot into USB thumb drive, secure boot?

[Rootman]

You need to enroll the key to the Secure Boot system.

Here is a nifty article on how to do it: https://www.technewstoday.com/ventoy-secure-boot/

Once enrolled it will allow ALL Ventoy boot drives to boot from that PC, at least until or unless the key is changed for some reason, then you will have to enroll it again on any PC you have already done so to.