Which version of LW is that? If 4.4 or above then try Tools>Options>Advanced>UPnP. If that doesn't work then Force IP instructions & sample image & 2 posts after that.

It'd be nice if the IT guy had have opened port 6346 on the system & modem/router to your computer. Without knowing the device brands & model no.'s I can't direct you to any specific instructions. There's 3 steps to port forwarding:
1. Static IP which you already have. 2.Forward a port in order to open port 6346 for LW.
3. Force IP within LW. (Instructions at top.)

If your equipment recognises UPnP tech then port forwarding wouldn't be necessary.