I've come across a number of 2220 boards and many Dell boards that were populated with defective Rubycon electrolytic caps. Recapped 16 such boards already and now they work just fine. Look at the motherboard very closely with a flashlight and see if any of the caps are swollen on the top where that "X" is cut into the top. Some may pop out the bottom. If any look like that then I suspect the board is defective. The 1800 ufd 6.3 vdc caps are notoriously suspect. They were counterfeits as well as other values on the board.

Do the green lights on the keyboard come on momentarlly when you reboot ot turn on the computer? Is it a USB or a PC type plug? Open the device manager and locate the keyboard line. Is there an exclamation mark over it? If it's a USB type try a different USB port. If it's a PC connector make sure it's not plugged into the mouse port. Then come back here and report your finding then we'll take it from there.