This is a new installation, and I was checking that Mobile Automation was working but I couldn't get logged in - I was getting "connect ECONNREFUSED".
I tried the X3 Services Sandbox (http://server-name/xtrem/explorer/) but I got the same error.
When I looked in the xtrem log file, I saw "Uncaught Exception thrown: Error: EPIPE: broken pipe, write".
The EPIPE error relates to X3 Services having trouble communicating with SQL Server - it assumes SQL has been configured to communicate on Port 1433.
I changed the tcp/ip port settings from Dynamic to 1433, and this resolved the problem.