E540 will not power on.

[The_Chimp]

Issue
My Lenovo Thinkpad E540 does not power on when pressing the power button.
The small red LED in the front does not come on either.

Background
Damage may have been done to the laptop while trying to debug an issue with a newly installed touchpad. This involved opening up the laptop and unclipping ribbon cables, including the one for the power button.
While the laptop was still open I reinserted the battery and tried to power it on (to allow for easy swapping of the new and the old touchpad while debugging). It would not power on at this point. (I know, this was not a smart thing to do!)
After reassembling the laptop, it would still not power on.

Steps taken so far
- Held down the power button to discharge the capacitor.
- Removed and reinserted the CMOS battery.
- Re-seated the power button ribbon cable after taking apart the laptop again.

As not even the LED on the front comes on, I figure it may be an issue with the power button or it's ribbon cable. I am really not sure though.
Right now the old touchpad is in the laptop. The laptop was working with the new touchpad however before trying to debug an issue with it.
Any suggestions on what damage might have been done, and any solutions to this would be greatly appreciated!