The server may be unavailable or the gateway may not be correctly configured.

Cognos BI 10.2.2 (or Cognos Analytics 11.0.x)
Microsoft Windows 2008 Server

You have not access to the Cognos Connection. The IBM Cognos service is running, what it looks like in Windows Services. The cogserver.log is empty since last restart.

Error message:
IBM Cognos gateway can not connect to IBM Cognos BI server.

The root cause, a corruption in the \wlp\usr\servers\cognosserver\workarea for WebSphere Liberty Profile (WLP)
Stop the IBM Cognos Windows service.
Backup the “workarea” folder.
Delete the “workarea” folder at  C:\Program Files\ibm\cognos\analytics\wlp\usr\servers\cognosserver\workarea
Start IBM Cognos service again.

More information: