Z590 Taichi no video in BIOS

I have the BIOS screen now.
I bought a new monitor - an Acer superwide 34" - and all I did was move the video cable from the old monitor to the new one.
Now everything's normal. I can get into BIOS.
It was the settings, I was running the old 4K monitor at 1920 X 1440, and the new one at the stock 3440 X 1440.
I switched the cable back to the old monitor and changed the settings to the stock 3440 X 2160, and can now get into BIOS with it, as well.
I guess BIOS doesn't like anything but stock monitor resolution.
Now I have an extra monitor...

Nothing has worked. I even upgraded from twin 3060s to a 3090 graphics card, and while I had the cards out tried to get into the BIOS with three different monitors on the motherboard port. No joy. The computer just refuses to output a video signal while in BIOS.
I don't get it, it was working fine, I didn't change anything, but one day the motherboard just quit displaying video while in BIOS. I was on the same monitor, same video port (motherboard), same cards, same everything. It just quit working.
All ports will put out a video signal in Windows, none will in BIOS. It's driving me crazy!

Nope, not yet. Since I'm running the monitor off the onboard graphics, I think I'll try removing the graphics cards. Maybe they're confusing the bios, I dunno.
I've been using ASRock motherboards since 2016, and this is the second time. The first one - Z170 Extreme 7+ eventually cured itself, maybe this one will too.
Perhaps if I leave a little barbecue in the bottom of the case overnight, it will make the gremlins happy.
Or else they'll invite their friends over.

This is weird. When the computer is shut off, if I hit the power button it boots into Win10 like normal and everything is fine.
But if I use the ASRock Restart to UEFI, or if I restart and tap the F2 key, either way, it enters UEFI (code Ab) but there is no video output. I've tried every video out port on the computer and no joy.
If I shut it off and restart, once again, it boots to Windows as normal.

ASRock Z590 Taichi
i7-11700K
128GB Corsair Vengeance DDR4 3200
Dual MSI 3060 graphics cards.
Display on motherboard graphics
WD Black SN770 2TB boot drive
2 Crucial 4TB NVME RAID-1
2 WD 10 TB Gold RAID-1

Can anyone help me figure out why there is no video signal from any port when it's in BIOS?
Trying every port on two graphics cards and the motherboard took a while.
This is driving me crazy!