title: Trust issue while sending a post to my API since DST Root CA X3 Expiration
body: <p>I have a C# api running on a aws S3 with ubuntu.
  This API is use by a website, a windows application and a xamarin app deployed on Samsung android devices.</p>
  <p>Since today 16:00 (paris time), the android part is not working anymore, I have a &quot;trust issue&quot;.
  Clearly it seems to be related with DST Root CA X3 Expiration (No release on my side and the timing is perfect).</p>
  <p>But I don't understand why...</p>
  <ol>
  <li><strong>SSL certificate</strong></li>
  </ol>
  <p>I checked my SSL certificate and regarding let'sencrypt forums, I have one of the path base on  &quot;ISRG Root X1&quot;. The second one is base on &quot;DST Root CA X3&quot; (expired).
  I renew them anyway to be sure, but still the same certificate path. (and no problem for chrome to contact them).</p>
  <ol start="2">
  <li><strong>Internet with https is working</strong></li>
  </ol>
  <p>I can reach internet with a webview inside the app (to my website in https)</p>
  <ol start="3">
  <li><strong>Can't connect using restsharp</strong></li>
  </ol>
  <p>When I use RestSharp to contact my server, I have the trust issue.</p>
  <p>My android devices are all the same: Samsung A7 tab, half up to date, the other half was update in august, all of them with Android 11. So theorically they are &quot;not concerned&quot; with this certificate expiration.</p>
  <p>Can the problem come from Xamarin or RestSharp ? Maybe my server certificate ?</p>
  <p><strong>EDIT</strong>
  Ok half resolved....
  If I go to the &quot;Trusted Root Certificates folder&quot; in my android device (don't know the exact name), If I disable the &quot;Digital Signature Trust Co. - DST Root CA X3&quot;, it's working again !</p>
  <p>Not a &quot;real solution&quot; since I need to update something like 150 devices...
  2 options in my mind</p>
  <ul>
  <li>Can I force RestSharp to use a certificate more than another ?</li>
  <li>Is it just because Android know the expiration date is 30/09 and still use it because we are still the 30/09 and everythin will work Tomorow ?</li>
  </ul>
  <p><strong>EDIT 2 resolved.</strong></p>
  <p>Thx to all of you, sorry I should have been able to validate this answer before some post, but stackoverflow was on readonly mode this night and I fall asleep after that.</p>
  <p>What I did (not sure if all step are mandatory).</p>
  <p>1/ I updated the certbot since mine was &lt; 1 (check with certbot --version)</p>
  <pre><code>sudo apt-get remove -y certbot python3-certbot-apache
  sudo snap install certbot --classic
  sudo ln -s /snap/bin/certbot /usr/bin/certbot
  </code></pre>
  <p>Procedure from @dmaehler from Letsencrypt forum</p>
  <p>2/ As @hamzaElHanna and @ThatCoderGuy said, I updated the certificates</p>
  <pre><code>update-ca-certificates
  </code></pre>
  <p>3/ I made a cert-sync to synchronise Ubuntu and Mono certificates (if it's working as i undertand it)</p>
  <p>4/ I renew my SSL certificate to remove the CA X3 since it's no longer in my server certificates</p>
  <pre><code>sudo certbot renew --force-renewal --preferred-chain &quot;ISRG Root X1&quot;
  </code></pre>
  <p>As proposed by @dmaehler and @jsoetewey</p>
  <p>SSlabs to check, the path with the old certifcate is removed and RestSharp work as previously.</p>
  <p>Thx for the help everything were usefull !</p>