I have a similar issue with GEP even though I have reset GEP so there are now no configured services I am still getting the error below.
I've used your utility and all indications are that the services are available.
I'm running 10.3 Arcgis Server and GEP on Windows 2012
Failed to create connection cxn-73279 com.rabbitmq.client.AuthenticationFailureException:
ACCESS_REFUSED - Login was refused using authentication mechanism PLAIN.
I noticed that there is a notice on the RABBTMQ - http://www.rabbitmq.com/access-control.html#loopback-users
That this process no longer allows guest logon against localhost.
This is the only thing I can think of short of uninstalling and re-installing GEP knowing that this issue may still exist on completion.
Have you ever seen this error?