SSL Certificate Chain Incomplete
<p>Can someone please explain what exactly the SSL Labs test's "This server's certificate chain is incomplete" means and how to fix it? Exact steps of what I did</p>

<ol>
<li>Generate Let's Encrypt certificate via the Let's Encrypt client using the standalone module (./letsencrypt-auto --standalone)</li>
<li>This yielded 4 files: cert1.pem, chain1.pem, fullchain1.pem, privkey1.pem</li>
<li>Generate PKCS12 file to import the certificate:   </li>
</ol>

<blockquote>
  <p>openssl pkcs12 -export -in cert1.pem -inkey privkey1.pem -out
  cert_and_key.p12 -name certificate -CAfile fullchain1.pem -caname root</p>
</blockquote>

<ol start="4">
<li>Create the keystore:   </li>
</ol>

<blockquote>
  <p>keytool -importkeystore -deststorepass Pas5w0rd123 -destkeypass
  Pas5w0rd123 -destkeystore cert.jks -srckeystore cert_and_key.p12
  -srcstoretype PKCS12 -srcstorepass Pas5w0rd123 -alias cert</p>
  
  <p>keytool -import -trustcacerts -alias root -file chain1.pem -keystore
  cert.jks</p>
</blockquote>

<ol start="5">
<li>Now using the created cert.jks on a server and having it tested with SSL Labs, the SSL test reports this problem: "This server's certificate chain is incomplete.".  </li>
</ol>

<p>Thanks very much in advance for your answers!</p>