The test connection to the Sharepoint server fails in the Sharepoint configuration panel in Confluence.
Confluence is deployed within a data-center or DMZ and is not able to access the Internet directly to make these requests. As a result, Confluence needs to go through a web proxy to make an outgoing request. The Sharepoint Connector has its own Web Service Client. This has not been tested with an outbound HTTP proxy configuration. See CSI-615.
If Confluence is not able to communicate with Sharepoint, disable the Confluence Proxy configuration.
Disabling outbound proxy will cause RSS macro and plugin repository client to cease working if Confluence is in a DMZ. To work around this, attempt to install plugins manually.