domain mapping plugin is mapping to incorrect url eg when it should be www.example.c

We are using Domain Mapping Plugin on our website ( but it seems that it is not working correctly. When user try to point their blog by setting up blog ip address.

Let me explain by the help of an example:

Our blog is running here: (Multisite Blog)

Suppose user 'test1' has got his blog url like

Now if user 'test1' login into his blog and set domain mapping plugin for his domain according to domain mapping manual(here

But when user test1 open in browser, it is pointing to main site that is not so can any one suggest what mistake that user test1 is doing ? or how can we avoid such issues ?