unable to add new servers to server groups

I am unable to add new servers to my server groups in pgAdmin. 

I have 4 servers already defined. I click the 'Add a connection to a server ‘, which brings up the New Server Registration dialog. I enter in the server information, username and password, click OK – and the connection to the database is not successful.

I have I have 4 servers already defined and I can edit the properties on those servers fine and save the changes– but can’t add a new one. The servers I am connecting to all use the same username and password credentials for my username, so I am confident in my user name and password. I am able to connect to the postgres server with other postgres clients (intelliJ database plugin, Valentina Studio client for mac), so the server is accessible to me. 

I can’t add a new server registration – despite having correct server name / host / port / database / username and password values defined. 

Using pgAdmin Version 1.20.0(dec 19 2014, rev. REL-1_20_0 )

Not compiled from source. 

OS X Yosemite 10.10.2