I decided to upgrade my Bela from 2.1 to 3.1, so I flashed the scared with the 3.1 image, bela boot just hangs with 4 leds lit.
So I reflashed 2.1 and the bela boots fine, I then copied this to emmc and it boots fine from there as well.
Reflashed 3.1, now bela boots from the emmc instead of the sdcard.
I seem to remember something about older BBBs needing something changed for 3.1? I can't seem to find anything on the forum though.