BeagleBone Green doesn't boot up

I’ve got a BeagleBone Green. Previously, I had burnt a Debian image on it. It worked fine and I was able to boot from the BeagleBone.

Following is my blog which shows the procedure of how I had Debian on BBG.

I wanted to have Ubuntu image on my BBG so I re-flashed it with Ubuntu image.

Following is the image.

When I gave power to my BBG, it started with blinking of all the LEDs simultaneously but then suddenly all the LEDs went off except for the power LED. I am not able to do anything now. LEDs are still off, only power LED gets on when I give power to my BBG.

I also tried to burn a new image on it as I thought that it might have happened due to the broken image. But nothing worked.

What could be the problem and how can I solve it?