Endpoint Protection

We have symantec v 12.1.6, we had to move clients to a new server and there are nearly 4000 machines.

https://support.symantec.com/en_US/article.HOWTO81109.html .

We used SEPM manager as dicussed above . From manager we could see that tak completed successfully and client log shows sylink.xml imported 

successfully. But client is still reporting to old server.

Was there a password set on the clients?

open the sylink on the failed clients and see whats the IP listed in there

If you have followed the steps in the below tech doc and taht did not resolve. Try the link TECH92556 and test resolving with the other 2 solutions.

1.
How to deploy/update communication settings from your SEPM to your SEP clients machines with SEP 12.1 RU2 or newer

https://support.symantec.com/en_US/article.TECH199124.html

2.

How to point clients to a new SEPM after decommissioning or replacing the primary SEPM

https://support.symantec.com/en_US/article.TECH92556.html

@ Brian - Yes, There is password.

Try removing it.