There are magic pressure points, ISTR they are about 3" in from the front and back of the unit (4 in total), you need to press in on the bottom half of the plastics to release an internal clip with gentle pressure lifting the top half - the top should pop off then.

Obviously, this voids your warranty, there is an exposed PSU inside which you shouldn't touch, no user servicable parts inside, etc etc. Disclaimer, disclaimer. My guess is that the display board ribbon has come adrift. If you do a power cycle, does the display light at all (and you just can't get it out of standby) or otherwise?

Hugo