Video problems with new build

Thanks for the thoughts, @magarity and @Ian.

So far we have tried:

1. reseating the card multiple times,
2. connecting the monitor to another computer (using hdmi, it works fine),
3. connecting hdmi and display port cables to the video card and monitor, every port on the video card (same problem).

We don't have a spare display port cable to try a different one.

Last night we booted up again (multiple times) and now the monitor just says "no signal". We took the video card back to Micro Center and exchanged it for a different video card (RTX 3060 TI), plugged it in and we're back to seeing the garbled display! Now I suspect the mobo is having a problem. I'm still very concerned, because it was a lot to spend for no result. And Micro Center says it will take like two weeks to diagnose hardware :-o

More ideas would be much appreciated.

Thanks

Okay, we discovered the problem. My son, who is the other part of we, had left the windows memory stick in the usb slot, so subsequent boots were evidently booting up from that usb(?). Anyway, after removing that from the usb, we were able to boot all the way up and update drivers, etc. It's all working now.

Thanks again @Ian and @magarity !!