You need to make sure you are downloading via Ethernet, not via Profinet (PN/IE). This setting needs to match in the control panel of the TP700 and the download window of WinCC.
The PN service is great for downloading on the local network, and especially for the initial setup of equipment. It is capable of searching the HW on the local network, and identifying compatible equipment there. You have the option to flash LED's on the equipment to ensure that you have selected the correct equipment. However, the downside is that it can only search or download to the LOCAL network. Profinet is not a routable protocol, because it operates at layer 2 instead of layer 3 of the network. Most VPN systems only allow for Layer 3 access.
The Ethernet download method, however, uses standard TCP/IP and can be routed to a distant system though a VPN. The downside is that you need to know the exact IP address of the target panel. Once the system is set up the first time, this is usully true. Everything should match what you have configured in the project.
I usually use the PN/IE downloads as I am first commissioning a cell, and then I switch to the Ethernet driver if I expect to do any remote commissioning later on.