Unable to connect to remote SQL Server instance after thorough troubleshooting
Something else you can have a look at is whether the TCP protocol for SQL Server is listening on the correct IP address(es). You can do this from SQL Server Configuration Manager.

Go the same screen where you enabled the TCP/IP protocol, in your case SQL Server Configuration Manager > SQL Server Network Configuration > Protocols for MSSQLSERVER and right-click on TCP/IP. Once the new screen loads, click on the IP Addresses tab, and you will see something similar to this:



The IP that you are connecting to remotely should show up in one of these fields (e.g. IP1, IP2, etc.). To find out what the IP you are using resolves to, run 
the following in a cmd session:  

    C:\Users\hs&gt;nslookup jxxxxxx.sxxxx
    Server:  UnKnown
    Address:  192.xxx.xxx.xxx

    Non-authoritative answer:
    Name:    jxxxxxx.sxxxx
    Addresses:  192.xxx.xxx.xxx &lt;- This is the address


By default SQL Server listens on all addresses, but in some cases, the default isn't used and addresses need to be explicitly added. Note that if you are using NAT or port-forwarding, you might not see the external IP, in which case you will need to work with your network administrators to make sure the translation or forwarding address is correct.