I have the same issue as what's described in this thread-
I installed FMP locally on the same computer as FMServer per this message on the thread:
'The only way the connection fails locally is one of two possibilities:
1. FileMaker Server has lost connection to our instance of a Web Server.
To test if this is the case, open a web browser on the server and type “localhost” to see if the “FileMaker Database Server Website” page displays. '
Nothing happens when I try to open localhost but I'm not sure what that means or what to do next...