I had this same thing happen, although with mine, it was after a (about 2 foot) fall. It could be software, but doubtful, since you can verify that by simply turning your phone off (not in standby, but completely off), and seeing if the battery indicator comes up when you start charging. Regardless, Google will ask you to do a hard reset before they'll replace it to ensure that it's not software-related.
As I said, mine was replaced under warranty for this very issue, so Google does count this as a replaceable issue (provided you bought it from the Play Store). However, there is one thing to try first:
Draw an imaginary line across the bottom of the letters in "nexus" printed on the back cover, and follow that line until you're even with the flash. Right there, there's a clip that most people miss when replacing the cover. That clip MUST be securely fastened, or wireless charging won't work (the purpose of the clip is to keep the wireless charging pins engaged). Press down at that spot to make sure that the clip is engaged.
Barring that, I'd contact Google for replacement (or your carrier, if you bought it from there).