title: Sudden "Cannot contact site at the specified url" error for no apparent reason
body: <p>I have a SharePoint site with a few subsites.</p>
  
  <p>I also have a C# program which connect to one of these subsites and import files to SharePoint. A few days ago, I installed this program on a Windows Server 2008 R2 SP1 Standard server (since it was mostly for test purposes, I just copied my project's bin/Release to the server).</p>
  
  <p>It worked flawlessly for a day, then, for no apparent reason, it stopped working. There has been no known changes on the server.</p>
  
  <hr>
  
  <p>I did some research, and conclude the issue could be linked to the DLL Microsoft.SharePoint.Client and Microsoft.SharePoint.Client.Runtime, since they were not initially distributed with my program.</p>
  
  <p>The program still runs fine on another server and on my machine, and I can access the SharePoint sites from the server using a internet browser, and of course from any other machine.</p>
  
  <p><strong>What I did try:</strong></p>
  
  <ul>
  <li>Including the DLL in my program's folder</li>
  <li>Deleting these DLLs from the GAC</li>
  <li>Reinstalling in the GAC</li>
  <li>Tried older versions of my program</li>
  <li><a href="https://stackoverflow.com/questions/23344032/im-getting-a-clientrequestexception-when-trying-to-get-my-libraries-list-share/23359157#23359157">Checked for outdated password</a></li>
  </ul>
  
  <p><strong>What I haven't/couldn't try:</strong></p>
  
  <ul>
  <li><a href="https://vasya10.wordpress.com/tag/cannot-contact-site-at-specified-url/" rel="nofollow noreferrer">Edit web.config</a>: I have no idea how to access it, since I don't have any known access to the site. Then again, the program works fine on other machines, so I guess the issue isn't website-sided.</li>
  <li>Reinstall .NET framework: If I can avoid doing this, I'm OK, but if there's no choice left...</li>
  </ul>
  
  <p><strong>The error</strong> remains the exact same:</p>
  
  <pre><code>à Microsoft.SharePoint.Client.ClientContext.EnsureFormDigest()    
  à Microsoft.SharePoint.Client.ClientContext.ExecuteQuery()    
  à MyNamespace.MyClass.getLibraries()    
  à MyNamespace.Forms.MainWindow.&lt;&gt;c__DisplayClass9.&lt;doConnection&gt;b__4()    
  Microsoft.SharePoint.Client/Void EnsureFormDigest()/Cannot contact site at the specified URL
  https://mydomain.sharepoint.com
  </code></pre>
  
  <p>Any idea on this issue? I will edit if more information is needed.</p>