title: SSL API request fails as of today: "Could not create SSL/TLS secure channel"
body: <p>we have a C# .NET 4.5 desktop application which was released half a year ago and ran fine until today. 
  On start-up the app sends a JSON request to our Web API but it fails with </p>
  
  <pre><code>{"The request was aborted: Could not create SSL/TLS secure channel."}
  </code></pre>
  
  <p>I have found some other topics where the solution was this:</p>
  
  <pre><code>ServicePointManager.SecurityProtocol = SecurityProtocolType.Tls12;
  </code></pre>
  
  <p>It works for our app as well but the big question remains:
  Why did it work on thousands of computers for half a year?</p>
  
  <p>The first thing I thought of was: Daylight Savings Time, the time change happened today. So I've checked the server time, renewed the SSL certificate and rebooted the server but the problem remains.</p>
  
  <p>Any ideas?</p>
  
  <p>App:
  .NET 4.5</p>
  
  <p>Server:
  Ubuntu 16.04.2 LTS
  nginx/1.11.10</p>
  
  <p><strong>Update</strong>
  After disabling Cloudflare for the domain, the issue is gone. I don't know what exactly causes this but I suspect that it has in fact sth. to do with DST time zone and SSL handshake. </p>