After instaling latest version in XP machines also stil agent not communicating to server it is shwoing offline

SEP 14 won't install on XP so for 12.1 follow these steps:

http://www.symantec.com/docs/TECH231025

Did you check the firewall ? 

are you able to telnet the SEPM server on port 8014 

whats the result of this?

How to test communication from an Endpoint Protection client to the Endpoint Protection Manager

https://support.symantec.com/en_US/article.TECH102682.html

Hello,

SEP 14 on XP machines?

Check this Article: https://support.symantec.com/en_US/article.TECH236004.html

Ensure that TLS communications is enabled for the clients

• Click the KB link and follow the steps in article TECH231025 to make sure that TLS is enabled on the Windows XP and Server 2003 clients.

Microsoft has discontinued the support of Windows XP and Server 2003 operating systems and is no longer patching or updating these systems.  These legacy operating systems are foundational are not capable of supporting the new protection technology and features, or the performance enhancements in Endpoint Protection 14.

Symantec strongly recommends that you replace these machines with a current Microsoft supported operating system for the best security and reliability for today's threat environment.

The Endpoint Protection 14 manager can successfully deploy, administer, and update the legacy version of Endpoint Protection 12.1 clients for these operating systems.  This mixture of versions is usually a temporary condition as the endpoints in the organization are upgraded.  In the case of Windows XP and Server 2003 endpoints, it may be necessary to use the 12.1 client until the computers running the legacy operating system are retired.