Resolve Unresponsive or White Screen
The first thing to do is power cycle the unit. There is a little tab that can be pulled off to power down the unit. For the FLEX, this tab is in the top right corner of the circuit board (circled below). It is important to note that the jumper should be pulled off with either your fingers or nonconductive tweezers.
For both the SRCM and MRMS, it is in the bottom right corner (circled below).
The SRPM is different in that it doesn't have a tag, but a terminal connector in the lower left that can be disconnected (circled below).
After powering down the unit, wait a few seconds and then return power to the unit. If the problem persists, there is something wrong with the hardware of the device and it will need to be sent in for repairs.