PC will not load Ventoy

[Hairy Mutley]

I had hoped that 1.0.12 Change the 1st partition active and 2nd partition inactive by default (compatibility improvement). might make a difference, but it hasn't helped.  Assuming that an Update is sufficient to do this, or do I need to do a re-Install?

I think that is enough. Try removing the bootable flag using fdisk and see if you're lucky as Tinkl

After 1.0.12 Update, fdisk showed that Boot was set only on partition 1; Ventoy not booting.
Used fdisk to clear the Boot flag on partition 1; Ventoy is still not booting.
For the heck of it I set Boot only on partition 2; Ventoy still does not boot.
Well... it was worth a try.