FIRST STEP: try simply turning it back on
Try turning it on as normal with the remote. does it work now? if not, the batteries (bad or sub-par quality batteries, 'get you by batteries', are included with the box for convenience but i recommend replacing them at your first opportunity) are possibly dead and if the box has buttons try the power button. if the box has no buttons try using good batteries from another [working] device, such as your tv remote control. does the box work now?
SECOND STEP: The Auto Power-Down 'Feature'
CECBs are required to be Energy Star Compliant and/or bear the logo. that also means they must have options which power down the box into what is called 'standby mode' which is also the mode used when the power is turned off by the remote or front panel of the box. it's also the very same mode used with Analog Pass-Through. on some boxes it's enabled by the factory at a pre-set interval ranging from 1-4 hours. it should also be in your box's manual, and it can be turned off or the interval changed in the menu itself. if the power off has become enabled while you were out or not watching, or it happened as you were watching, don't panic. why there is no warning i do not know, but try turning the box on as in step 1 above, and if it works, that's what happened. when on the boxes use a paltry 7W, no more than a nightlight bulb. so why they need the 1W power save function is beyond me.
THIRD STEP: The Master Off/On Switch
I don't know why, but some boxes have a 'master on/off' toggle (not labeled) on the side or rear of the box, with '1' and '0' labels or 'on/off' labels. it turns the entire box off even when plugged in. if the box has become 'dead' after it has fallen, it could have simply fell on the switch and inadvertently turned the switch off. i do know the Magnavox converter has this switch on the right side.
FOURTH STEP: The Ground Fault Circuit Interrupter (GFCI)
Most modern homes, travel trailers, mobile homes/manufactured homes, RVs, etc have these as some sort of protection from hazards such as moisture in bathrooms while using bath appliances, or kitchens while washing dishes, or outside for protection against rain shorting them out. some garages also have either all of them this way or a couple by a work bench or near a source of water. they are usually just normal-looking outlets with a red 'RESET' and a black 'TEST' button. some have only a 'RESET' button, and the buttons can even be white and even bear a LED which lights when the outlet has tripped for whatever reason. sometimes one can be in an entertainment area or in the room where your TV or converter exists. why i do not know, and i normally frown on these kinds of outlets with a passion as they cause more trouble than they're worth. they trip with no load, and some are wired in series with other parts of a home, including outlets in a room next to it, or even the lights in a hallway, or even half the house itself. For example, in a kitchen the GFCI can trip and take out the microwave, stove, or even the living room outlets too. if your TV has gone out this may have happened (or the main breaker tripped--check it too)
In some cases the GFCI trips and only one outlet fails. the other works fine. which means if the TV works but not the box, and the box is plugged into one of the two outlets within a GFCI, or vice versa, this may be the culprit.
To verify it was the outlet, or to check the other GFCIs in attempt at finding the reason the outlets apart from it have failed, bring a small lamp with you and push the 'TEST' button (if applicable ) and listen for a CLICK from the outlet. if it does, push the RESET button and verify power with the lamp. if the lamp works try the box or TV again. if not try the other ones. if for some reason you don't hear a click from a GFCI, try pushing in the RESET button (could have tripped causing your issue) if it does engage and you have power now to the lamp and your issue is resolved, great! if not and the RESET button continues to trip or immediately pops back out, your outlet is faulty and a qualified electrician must be called for adequate repair. DO NOT FIX THIS BY YOURSELF!!!
FIFTH STEP: The Surge Protector
Most people today believe in protection from power surges from lightning storms, or brownouts (which they normally buy a Uninterruptible Power Supply (UPS) for the latter) which can damage electronics, and HDTVs, Converters and most modern electronics are no exception. these strips and power supplies normally incorporate a small circuit breaker, two LEDs (Building Wiring Fault/AC Power) and an on/off switch (sometimes the breaker as well). when working they have their 'surge protected' outlets (labeled normally, some only have a select few protected outlets esp with UPSs since they also use those for the battery-backup) powered and the only LED lit being 'AC POWER' or a plug icon, or the on/off switch has a built-in lamp. if the issue causing your no-power situation has been caused by the strip or power supply, either one of a few things has happened. if the on/off switch or power LED is not lit, the strip may have tripped to protect your electronics, or in the case of a UPS, the battery may have become faulty and the unit shut down to prevent problems. if this has happened the 'protected outlets' will have no power or all of them won't. if the 'SITE/BUILDING WIRING FAULT' lamp is on, the protected outlets won't work and sometimes neither will the others, but sometimes the non-protected ones will. this means that for some reason the neutral leg of the outlet which the strip is plugged into has no power or has crossed into earth ground. or earth ground is missing in the outlet or someone without proper electrical knowledge cut the 'third prong' from the plug to make it fit into an older outlet without the third pin. in those two situations replace the strip or repair the outlet (electrician again, this is NOT a DIY if your home's wiring is involved!!!)
EDIT: HEAT RELATED ISSUES WITH CONVERTER BOXES
Some converters posted with issues recently have had heat-related failures or problems which ultimately lead to failure. i've found that using a CPU fan from a older computer lying around or bought from good will for parts, sans heatsink (fan screws onto the heatsink and is easily removed) would work wonders for cooling down a converter box as a chassis fan, as most heat seems to be around where the power supply portion of the box is.
1. small phillips screwdriver
2. an old CPU fan
3. some wire snips/strippers
4. a 12VDC wall wart, aka a AC/DC adapter
5. dremel, or other rotary tool
6. any drill and the smallest bit
7. four (4) small 1/4" wood screws. usually one can find these where you get hardware to hang pictures with
8. a DC Multimeter
9. two (2) butt connectors of the smallest size
first, use the screwdriver to remove the fan from the heat sink. four tiny screws usually hold it in place. next, remove the cover to the converter box. be careful that it is unplugged, and allowed to sit a 24-hour period after being unplugged before removing the cover (some boxes have highly charged capacitors which can deliver a lethal or dangerous shock even after the box is unplugged)
Next, use a dremel to make a tiny square vent, but just smaller than the CPU FAN itself. use the drill to drill the holes needed for the fan to line up. use the fan and place it to verify where the holes need to be. these will be so you can use screws, but longer screws than the fan came with, to hold the fan in place.
Next, use the wire snips to cut off the plastic connector the fan has on the end of its wires. then use the strippers to shave off 1/4" of insulation from the wires. usually the positive wire is red, and the negative wire is black. use the multimeter to determine, with the wall wart plugged in, which wire is negative, and which one is positive. drill a medium-sized hole in the rear of the box just large enough to pass the wires from the wall wart to the fan inside. then connect the fan to the wall wart using butt connectors.
Now, you have two plugs for the box. one for the box itself, the other for a fan. you can also change the steps a little if you're more experienced in electronics. some boxes may have a pre-placed fan connector inside, but unused. some don't. as usual, steps may vary depending on the converter.
SIXTH STEP: The box could be faulty
If you have tried all these troubleshooting steps and still are in the same boat, no power to the box, the box could indeed have failed. some are manufactured cheaply and do indeed live a short life. the reason i have saved this step as last is because most people falsely blame the converter from the get-go and that's normally not the case for a properly functioning box to suddenly go dead like this. most start having software issues or have trouble with normal operation or emit noises during operation before failing. but that doesn't rule it out as a possible cause. coupons don't give refunds and most retailers won't refund the boxes and only give exchange for same or similar item, and for that i would recommend this board for the reviews of boxes to find a similar one that is known to be of good quality. you may pay more but it's worth it in the end, trust me!