I’m having the same symptoms as the OP. In my case I was trying to boot with MMC, and can’t see any output on serial console (maybe it’s my UART cable). Green LED turned on, but blue LED never turned on after a long wait. eMMC was partitioned correctly as I can verify them on a Linux machine. Both Linux and Windows can’t see any devices in maskrom mode (green LED on).
I’ve contacted Allchina and they suggest this might be PD issue, so I tried a fixed voltage DC 12V 3A barrel jack to USB-C, but same symptoms as with PD…