This should work if the servers are in a domain. If not in a domain but using a workgroup setup you will have to define a user and use it instead of network service.
This is not a development issue and therefore I am guessing you will get much better help by partners active on the Support Community. If the knowledge base articles does not help please try the Support Community - https://force.milestonesys.com/support/MccSupportCommunity
we have tried reinstalling of latest mobile server but still mobile server is not connecting to surveillance server. We tried with user and password also.
This was working fine before. Once we restarted system the problem arise.
Mobile server does not starts automatically on system re-start, while all other milestone servers starts.
I had this same problem, my solution was that Milestone Image Server service was not running, once it started I restarted I restarted the mobile server service.