Just purchased a Phantom 4 Pro and have not been able to charge the battery or get it to turn on.

Hello and good day sitework1702. I am sorry to know about the trouble, with regards to this issue you may give a try to charge it for a while it seems the battery is on the hibernation mode and wait. If ever still will not charge. I would suggest reaching out one of our support channels in order to guide you on what you'll need to do. You may just go to this link https://www.dji.com/support Thank you for your support.

I have had it on charge all day and no sign of life.

From what I remember, when in hibernation mode, the procedure is to push the battery button once, then set the battery down and don't touch it for at least five minutes.  Then after five minutes, plug it into the charger, plug the charger into the A/C wall socket, and wait.  If you're lucky, it will eventually begin charging.  It might take an hour or two to blink.  Otherwise, it's DOA, which happens sometimes.  These batteries are not engineered to sit for long periods without some attention.  

Good luck

Not uncommon to get a DOA battery, if you are confident you are doing everything correct, return it. Don’t waste time trying to revive it, if you succeed in bringing it to life, you’ll never fell comfortable with it. Don’t lose faith in DJI, it’s common with all lithium batteries.