On one off my machine I have a similar problem with MCP over Ethernet. The machine run well for some years.
I check with Network System Center to check system dhcp, dns, OPs...
When I do that the error disappears and the MCP connect.
Check IP address with VNCScanner (uncheck port 5900).
What shows the file in :\user_base\Services\udhcpd\var\lib\misc\udhcpd.leases.
In this file you will find mac address, IP, DNS name for your MCP
On my machine the problem is a know DNS problem and I need to upgrade to PCU Base Version 8.2.