3200 Will not power up?

Have a 3200 that was dropped, casing came off and power button dislodged.
Have taken it apart, cleaned and checked for loose bits !!! Put it back together, but now it will not turn on.
Screen is okay - can see charging bar come on if you plug it in.

Suggestions on how to go on or where I can get internal diagrams / schematics to better check if something broke ???

TIA