Hi
First of all, check that the dns configuration is correct on the TMS and the VCS. Do an nslookup of the TMS servers FQDN in the commandline and see if it resolves to the correct ip. Do the same on the VCS (login via SSH as root).
If it resolves correctly, go to the admin tools, config, network settings and check that the IPv4 address and TMS FQDN matches the TMS servers actual settings.
If they match, reboot the TMS server and the VCS and try to re-enable it again. A couple of questions:
Is the TMS server added to a domain?
Is the TMS and the VCS on the same subnet?
Have you enabled replication on this VCS before or has it been working before at all?
Make sure the VCS is tracked by hostname.
If none of this helps you, please raise a TAC case on this.
/Magnus