MacBook Pro will not start up

A friend brought me his 15" MBP (2007 Core 2 Duo 2.2 ghz, i think) saying when he tried to turn it on one morning it did nothing. He had no problems before. We looked it over and saw that the power button was collapsed slightly. He has kids that like to stress test everything, so we thought one of them had mashed it too hard and damaged the button.

I ordered and replaced the top case because it includes the power button. However, after replacing it the MBP still does not boot up. Same symptoms. No noises, no lights...nothing happens when the power button is pushed.

I tried resetting the PMC (?) by holding down the control, option and command keys then holding down the power button for over 10 seconds. Nothing.

I did not remove the memory when I replaced the top case so I do not believe this is the problem (some other posts suggested re-seating the memory modules).

The replacement went smoothly except for re-inserting the keyboard ribbon into its slot. The ribbon was too flimsy to slide in by hand. Using a magnifying glass to align the ribbon with the slot, I used a spudger to gently inert it in the slot. It was hard to tell if it seated very deeply, but the ribbon held fast against a little tug, so I believe it was seated properly.

After the replacement, I plugged a magsafe charger into the port and the green light came on. The battery lights indicated only a 2 or 3 dot charge, but the orange light did not come on to indicate charging. I let it "charge" overnight and the next morning there was no change to the batter status lights, or the charging light. I did not check this before making the replacement, so I do not know if this condition existed prior to top case replacement.

Questions. (1) Is there a known problem with boot failure after installing the top case in this model? (2) If the boot failure is not based in the power button / top case, what else can I check?