If you find your board does not work or stops working, here are a few things to look at.

Are there lights on anywhere? There should be a light on the 12v regulator board (the bigger one on the bottom left) and on the DAC (the board on the bottom right). There also should be lights on the pi itself near the SD card. If there aren't odds are you blew the fuse. Test with a multimeter or replace the fuse. The fuse is a normal 5x20mm 250v 1A fuse.

Check the output voltage of both of the regulators/buck converters. The left one should be outputting 12v and the right one 5v.

The screen is controlled off of the pi. It will not come on unless the pi has fully booted up. If it's not coming on, make sure that the pi is coming on. There are lights near the corner by the SD card. If they are on, then there is an issue with the firmware image or the SD card itself. Make sure the SD card is from a reliable retailer and of a good brand. There are a lot of Chinese cloned SD cards out there that are junk. If the screen still doesn't come on, its usually easiest to hook up a monitor to the pi and see what's happening.