This site is being deprecated.
Please see the official X‑Plane Support page for help.
I'm not with Laminar Research, just a fellow simmer in the UK and I suspect that when you are trying to install the DVD's, X-Plane 11 is automatically attempting to make contact with LR's website to download the X-Plane 11 Installer.exe application, which is a separate program and required to complete the overall installation.
Please advise if you already had the X-Plane 11 Installer application installed on your PC before loading the DVD's?
Also, it may assist you by clicking on following link for instructions on how to install X-Plane 11 correctly from DVD's:- https://www.x-plane.com/kb/how-to-install-x-plane-from-dvd/
This site is no longer being actively maintained.