Trouble booting Rock Pi 4 B

Hi there. I’m having trouble booting my new Rock Pi 4 B. Here’s what I’ve done so far…

  1. Flashed Ubuntu 20.04.4 to a 128GB Sandisk Extreme uSD using Etcher
  2. Plugged in keyboard via USB 2.0 to RP4
  3. Plugged in mouse via USB 2.0 to RP4
  4. Plugged in monitor via HDMI to RP4
  5. Inserted uSD (the correct way) into RP4
  6. Plugged in included power cable.

I get a solid green LED light but no other response.

I’ve double-checked that my monitor works, that the uSD is facing the right way, and I’ve tried Raspberry Pi OS and Twister OS. Each time, I’ve successfully flashed the OS to the uSD, according to Etcher. I’ve also switched the switch behind the USB from “L” to “H”, as was suggested on another thread.

What am I doing wrong here? Do I have a lemon?

Did you download your image from here https://wiki.radxa.com/Rockpi4/downloads ?