What does it mean if from OpenCore I get a prohibited sign then right back to the picker?

Hi, hope all are well!

This was a crazy one today. Actually been seeing it on my other build too but basically

I did a new build today with identical parts as before, I have the EFI backed up. Generated a new smbios and it would just prohibited sign and go back to the Opencore picker. It didn't give the waiting for root device error. With verbose it said exiting efi boot.

Eventually I redid the whole opencore config from scratch and it worked, well. Semi. Turns out the issue was partly because I was using hdmi with IGPU on a 4k tv. Worked fine with a 1080p one.

Anyway, what does this mean? I'd like to be able to better address it in the future

Thanks in advance!