Installing EP on desired AOS ( Enterprise Portal installation, 'AOS´XXX# cannot be reached' )

While trying to install the Enterprise portal I came across the following error on the setup :

The AOS 'Name@2712' cannot be reached. Setup cannot continue.Verify that you entered the correct server information an that the AOS is running.

This error is basically because the SetupSupport files pick the wrong/previous/deleted configuration for the Setup. The trick here is that along with the configuration what we fail to update is the Business Connected Proxy Account on the configuration, which normally points to the old server.

Solution :

Navigate to The Client Configuration from Administrative Tools, and change the Client Target to Local Client , and change the configuration to point to the correct AOS.

Navigate to Client Configuration Again, and change the Client Target to Business Connector, and point to the New AOS. 

In some cases
System Admin > Setup > System Accounts had different account mapped. correcting this resolved the issue.

Hope this helps