In some instances, you will need to remove the Touchscreen from the wall to aid in troubleshooting. It may be easier for two people to complete this process. 

First make sure the screen is fully powered down and turned off at the plug. 

Now simply unscrew the two small L-Shaped brackets on the bottom edge of the screen. Once these are removed, the screen can be lifted from the wall, like a picture frame. 

Cables are plugged into the back of the screen, so be careful not to move the screen too far away from the wall until you have unplugged them.