A stock display settings are set to 720p and if you have some extraordinary display, you need to login via serial or network and then use h3disp utility to set correct one, but first ... strictly follow procedures written in Getting started. SD card and power problems are very common and their symptoms can also show this way. Make sure you use Etcher for writing or check what you write. DD doesn't check and SD media is can be crap.
Wait a minute and you should see a login prompt. You need to create a normal username if you want to run a desktop. When you do those things, desktop starts automatically.
normally a blinking led should show that the system has bootet (heartbeat led).
Maybe you could try to use etcher for Linux or Windows to create the bootable sd-card? https://docs.armbian.com/User-Guide_Getting-Started/#how-to-prepare-a-sd-card
