1.  Is ServerA and ServerB two Sharepoint web front ends of the same farm?  Or two seperate Sharepoint farm?

2.  Was the K2 for Sharepoint 2010 components installed on both of those servers and features activated?

3.  Perhaps there are some firewalls that are blocking communication on default K2 port 5555, 5252 or Sharepoint web ports (80. 81, 443, etc.)

Thank you for the reply.

1.  Is ServerA and ServerB two Sharepoint web front ends of the same farm?  Or two seperate Sharepoint farm?

Ans.Yes both the server are from same farm / domain.

2.  Was the K2 for Sharepoint 2010 components installed on both of those servers and features activated?

Ans. Yes

3.  Perhaps there are some firewalls that are blocking communication on default K2 port 5555, 5252 or Sharepoint web ports (80. 81, 443, etc.)

My doubt is previously I had register service instance of document library of server A into server B, and I am currently using that too.But whem I am trying to register service instance of new document library it is throwing me an error.

PFA, I have attached the error message which I am getting.

Hello,

Is the SharePoint server where the L3 resides configured for SSL. If so ensure that there are no certificate issues when trying to connect to the server.

Thanks

Lubna