First, I have to commend you for having a really fine piece of equipment. Mission makes great products. Now down to business. Being where I am and not being next to your sub-woofer with test instruments and tools I'm going to be so basic as to almost be insulting. However, If I were there, I would be testing these things.
Normally, when one has a catastrophic failure. i.e. no power, and no indication of power present one starts with the power supply. And that starts at the power company.
1st Determine if there is power in the actual outlet that the unit is plugged into. I have found that when installing a sub-woofer on a two plug wall outlet, for example, it might be plugged into a plug intended for a floor lamp. and is turned on and off by a wall switch. Many residences have this feature. It is usually one of the two plugs in an outlet. So you have to test the actual physical outlet. If the outlet is off, check the light switches. If there is no power to the outlet, check the household circuit breaker.
Let's assume that everything works, so far.
The next thing to do is check the internal fuse with a meter. If you don't have one, pick up a multimeter from Radio Shack or Walmart for less than $20.00 or Harbor Freight for less than $7.00
If the fuse looks good but checks out bad (sometime happens) replace it with A FUSE OF THE SAME VALUE. DON'T STICK IN A PIECE OF ALUMINUM FOIL OR BYPASS THE FUNCTION AND PURPOSE OF THE FUSE.
The fuse costs a dollar, at the most, the Sub-Woofer costs $800.00 at the most.
OK, so now you have either a working sub-woofer, or an elegant paper weight.
If it is still being a paper weight, contact mission to locate an authorized service company. This piece of equipment in not designed to be user servicable
Here is their link below,
I hope this helps,