Radxa Zero boots but NO HDMI OUTPUT AT ALL. HELP!

I got a USB->TTL serial adaptor and hooked it up to see what, if anything, was happening.

At first it didn’t boot, saying that it couldn’t find any partitions. On the second go it did boot, but it outputs no HDMI. Imagine my surprise when I found that I could log in via the serial TTS via Putty.

I thought maybe I could use xrandr to force a display resolution, that it might be trying to output something my monitor can’t do, but this idea did not work.

xrandr --listmonitors

returns

Can’t open display

I think my unit is defective. What do I do now?

Which image did you flash?

I’ve tried every one available, but at the moment I’m running the Radxa distro of Debian Buster.