This site is being deprecated.
Please see the official X‑Plane Support page for help.
I have always had to use the xsaitekpanels plugin to make them work.
Go to this link
you can download the zip file, there is a pretty length manual along with the code.
By the way, I did see a post from Sparker, the author of xsaitekpanels, that he tested the plugin with X-Plane 11 and it was working. Here is the thread, his comment is the first post in the thread.
This site is no longer being actively maintained.