This P4P V2.0 was opened and flown once when I bought it.  How do I register this product to my account so I can get the warranty and by the DJI Care Refresh?  Thank you.

You should get the option to register it when you have internet connection and connected for the first time to the drone.

You can't register a drone twice/between profiles. Once it's activated that's it. You can of course use it on the GO app using your profile but the icon won't show on here as previously activated/second hand.

Hi there, the drone can only be activated once, and it must be activated before flying. If you activated it with the same Forum account, it shall be displayed under your Avatar, if not, please PM me your serial number.
DJI Care Refresh can be purchase directly before you activate the drone or within 48 hours after the activation, if it has been over 48 hours, you will need to take a video to verify your drone is still in good and working condition, here is the video sample for your reference: https://repair.dji.com/en/djicare/customerupload Once you take the video, pelase send to djicare@dji.com for further assistance.