I have the same issues.
My board ‘appears’ not to boot up, when connected nothing displays on the monitor.
I can install boot into the SD CARD install images, install both Android and IOT core. The IoT image boots but the Android image appears not to boot.
I have watched the videos, realised it may talk longer to boot when booting the first time. Used fastboot to flash Android and still i get the same experience, almost like android does not work on the device
Is it possible that Android does not work ? or is not compatible with the versiopn of the dargonboard i have ?