Mr Duke, this sounds like either you've either:

1. Entered the SageCRM url incorrectly into the connection string of the System Connector or...
2. (More likely) Tomcat isn't running or has an error.....the CRM Connector uses tomcat entensively (SData), so if this isn't running you'll get a 404 (or not found) error. To check that Tomcat is running enter:

http://[server]/sdata/[sagecrminstance]j/sagecrm/-/$schema

Replacing [server] with the server name and [sagecrminstance] with the instance name.

Closed due to inactivity.