Either your battery need to replaced or the connector is loose. If the connector is loose it it need to be replaced or desoldered. Send it to a repair shop OR fix it your self. https://m.youtube.com/watch?list=PLGN8VD... For the connector. What I would do is to diagnose the problem by dissasembling it.
This video should help you. This does NOT look easy to disassemble. Watch it from start to finish. It looks like the hinge is on the screen. You have to take most of it apart. Try to not break anything. If you need to replace the hinges use the eBay link down below. This includes the brackets. Video of disassembly (set it to 720p): https://m.youtube.com/watch?v=K-pTfjelLB0 Hinges: http://www.ebay.com/itm/HP-ProBook-4420s-Left-Right-Hinges-and-Brackets-60-Day-Warranty-/331314216278?hash=item4d23ddbd56:g:RvgA...
Needs to be more specific. Was the ribbon cable or the ribbon connectior broken. If possible show an image of what it looks like. Either it is a loose ribbon cable or a broken connector.
Camera ribbon cable is very brittle, be careful.