I have tried scanning with Probe, both windows domain and network scan. The workstations are found but all of them have error saying that the connection parameters are wrong.

I have double and tripple checked them and am 100% sure they are correct.

Computer management, WMI control on the PCs shows the error that the RPC server is unavailable.

I suppose this has something to do with it. How do I switch on the RPC Server?