If it's totally dead I'd crack the cover and look for fuses around the power supply/where the power cord plugs in the back. Might be as easy as a fuse, note you may need to remove some type of cover once you've removed the units outside cover.
If you have a volt meter it will make testing much easier. Before even removing the cover I'd measure for voltage at the female end of the power cord, it should unplug from the back of the E85H.
Depending how many "months" its been unplugged, you could have an issue of the backup battery going dead (this provides a trickle of current lasting many months to a few years, preserving the recorders start-up data when its unplugged). Since the EH85 is a relatively recent model, its probably too soon for the battery to have exhausted, but you never know. The most likely cause is a blown fuse, as jjeff advised. A Panasonic with a good fuse but faulty power components usually turns on and displays an error message, or turns on but refuses to do anything. Completely dead would indicate checking the fuse before going further. Good luck!
I just did a capacitor replacement C1210 and 1211, I believe. Control hard drive functioning. The fuse is real simple to replace, but if memory serves me you may still have to remove hard drive and the bracket to get to the power supply board the fuse is on. If you have capacitor replacement, it wasn't that bad, and I've never soldered on a board. Be extremely careful in getting the old capacitors off, that is the hard part where you are more likely to damage the board with too much heat. Getting the new ones on is a piece of cake after that.
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