Product:
Cognos TM1 10.2.2
Cognos BI 10.2.1
Windows 2012 server

Symptom:
Can not login to TM1 Architect when changed to CAM security.

Error message:
SystemServerClientNotFound

Cause:
The firewall on the Cognos BI server is not letting port 9300 though.

Check the value ServerCAMURI=http://servername.domain.com:9300/p2pd/servlet/dispatch
in TM1S.CFG file on the Cognos TM1 server.
Copy the value http://servername.domain.com:9300/p2pd/servlet/dispatch
and paste it into Internet Explorer to try to surf from TM1 server to BI server.

If it does not work, check the local firewall settings on the BI server.

Go to Control Panel\All Control Panel Items\Administrative Tools
select Windows Firewall with Advance Security.
Select Inbound Rules.
If there does not exist a Cognos TM1 rule, create one.
On local port set 9300, and on remote port set All ports.
Save the Rule.
Test again to surf to BI server from TM1 server.

This are the most common ports you need open for Cognos BI and TM1;
25, 5495, 5498, 9300, 9510,12345, 49152-65535

You get also the same error if you misspell the server name in ServerCAMURI

More information:
http://www-01.ibm.com/support/docview.wss?uid=swg21459257
https://www-304.ibm.com/support/knowledgecenter/SSEP7J_10.2.2/com.ibm.swg.ba.cognos.inst_cr_winux.10.2.2.doc/c_reviewthedefaultsettings.html%23ReviewtheDefaultSettings