Any computer on the internet can be addressed by its IP address. Those IP address are commonly called "public IP address".
Internet servers have public IP addresses.
Nowadays, desktop or laptop computers are typically not connected to the internet directly. They have internet access through a router using a technique called IP masquerading (or NAT). Using this scheme, computers get assigned a "local IP address" such as 192.168.., 172.16.. or 10...*. Those addresses are invalid on the internet. Only the router has a valid public IP address.
A client with a local IP address (behind a router) can always establish an connection with a server using a public address (directly connected to the internet). That's why web browsing works perfectly.
However, if both parties are behind such a router, i.e. none of the computers has a public IP address , establishing a connection is impossible.
You have several options:
- Establish the connection through a server (as it is done with TeamViewer)
- Configure one of the routers to make incoming connections possible (port fowarding)
- Establish a VPN. Minimum requirement is that one of the routers allows either port forwarding or supports some VPN (or connect through a third party server).
Please research the network situation of your office. Find out, whether your IP address is public and, if not, who controls the router. Then, ask whether port forwarding or a VPN is an option they can provide (or consult the manual if you have access to the router).