> Invalid address. Your business address must be a valid physical address from which you conduct business and cannot be a P.O. Box. This address is not shared publicly and can be your personal address. You may use a P.O. Box as your customer support address.
So in other words, a personal home address should work.
Although its odd your error message is seemingly saying a personal address doesn't work, unless "private mailbox" means a privately rented commercial box, like UPS