I'm not with Laminar Research, just a fellow simmer in the UK, but a couple of questions if I may:-
1. Is your copy of X-Plane 11 from Laminar Research's website (or DVD set), or is it from Steam?
2. Are you trying to update using the X-Plane 11 Installer.exe application, when you get this message?
3. Can you upload a copy of your X-Plane 11 Installer Log.txt file to this Q&A post? If you're not sure how to do this, please click on the following link to view some instructional PowerPoint slides that I have put together:-