I ran into a an issue today. When I tried to add a user to a site in my SharePoint 2013 site, I got this error:

Sorry, we’re having trouble reaching the server

A google search gave these two possible solutions:

• More RAM
• Using Display Names

I know it can almost everything that can cause this error. Here are my two öre :) I found that when I tried to add a user, an ajax call was made. And this was the error:

For a while ago my colleague gave me a nice tip of getting the right absolute url regardless sharepoint zone in Alternate Access Mappings. I want to share it, because it is brilliant:

var url = SPUtility.AlternateServerUrlFromHttpRequestUrl(new Uri(value)).AbsoluteUri;