Rockpro64 doesn't boot

[daimon]

I recently received a Rockpro64 board and am having difficulty getting it to boot. I've searched through the forum and haven't found quite the same issue. The board itself is the 4GB version with a 20 mm heat sink, no eMMC module installed, powered by a 12V-5A power supply. and labeled V2.1 2018-07-02. The keyboard and mouse are both USB and an HDMI monitor is attached, as well as an Ethernet cable.

I used Etcher to try the following images: bionic-minimal-rockpro64-0.7.9-1067-arm64.img.xz, bionic-lxde-rockpro64-0.7.9-1067-arm64.img.xz, and stretch-minimal-rockpro64-0.7.9-1067-arm64.img.xz, but none has booted. When power is applied, the green LED comes on but no other LED lights up, not even the Ethernet one, and nothing appears on the monitor.

I've tried several microSD cards, all with the same result. I do have experience burning system images, having worked with Raspberry Pi systems. In fact one of the microSD cards I tried was previously used in a RPi2 both before and after the Rockpro64 attempts.

Does anyone have an idea of what to try next? Are there any checksums available for the download images?

Thanks.

try stretch-minimal-rockpro64-0.7.11-1075-arm64.img.xzWhen I received rock64pro and tried to boot it, I tried the 4G, 16G, 32G SD card. The combination of the 32G SD card and the stretch-minimal-rockpro64-0.7.11-1075-arm64.img.xz can now be started. I am using dd to copy IMG under linux.