Question Monitor not recognizing computer signal?

Sep 1, 2020
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I bought a new monitor for an 8 yo HP Pavillion 500 desktop (don't remember what's in it) last Xmas, worked like a charm. The HP didn't have an HDMI output, only VGA and DVI, so I used a DVI > HDMI cable, worked fine for months. I left to quarantine elsewhere for a while, came back and the monitor now doesn't recognize the computer's signal.

Monitor works fine, I can connect my laptop to it no problem, but when I change the input to the port assigned to the desktop, monitor reacts as if nothing's there, even though the computer is clearly booting up. I tried all the usual steps - turn off/turn on, unplug/replug all the cords, and nothing. Of course I threw away the ancient monitor to confirm that the booted up HP is producing a signal, so I have nothing to compare it to. Thoughts?
 
Can't download the driver update without a monitor. Short of getting another monitor, any ideas? FWIW, this has happened before, but a simple turn off/turn on worked fine.