Well first off, if you purchased your surface pro 2 power cover from a reseller like Amazon, then there's a good chance your power cover won't perform as you want it to. As benjamin.hua explains, he hasn't been able to get his to charge despite trying to wake it up. I've bought and return two with no luck. It's like the reseller doesn't care if you buy and return for free on Amazon. Many complain that these units, upon calling Microsoft, are actually refurbished units far beyond their warranty period. The battery in the cover has been sitting discharged for weeks, months, even years so even if you get the Surface to recognize the cover, it won't do much more than be a heavy keyboard. BTW I'm typing on my surface with power cover. No the battery doesn't charge.
To address the issue of recognizing the keyboard, have you check device manager to see if it shown as an unknown device? Also try updating the firmware and windows update on the surface. Good luck!