Product:
Cognos Analytics 11.0.13
Microsoft Windows 2012 server

Problem:
Problem to login in Cognos Controller after TLS 1.2 demand on the CA11 server is implemented.

Error:
The underlying connection was closed: An unexpected error occurred on a send.
at System.Web.Services.Protocols.WebClientProtocol.GetWebResponse(WebRequest request)
at System.Web.Services.Protocols.HttpWebClientProtocol.GetWebResponse(WebRequest request)
at System.Web.Services.Protocols.SoapHttpClientProtocol.Invoke(String methodName, Object[] parameters)
at Cognos.Controller.ControllerSoapHttpClientProtocol.Invoke(String methodname, Object[] parameters)
at Cognos.Controller.Proxy.Light.WSLight.CheckServerConnection(String sGuid, String sUser)
at Cognos.Controller.Direct.ServerInfoD.CheckServerConnection()
at CCR.AppContext.CheckConnectionToServer()

Solution:
On cognos controller client computer
start a command prompt as administrator
Run below commands (to update the registry)

REG ADD HKLM\SOFTWARE\Microsoft\.NETFramework\v4.0.30319 /v SchUseStrongCrypto /t REG_DWORD /d 1

REG ADD HKLM\SOFTWARE\WOW6432Node\Microsoft\.NETFramework\v4.0.30319 /v SchUseStrongCrypto /t REG_DWORD /d 1

More Information:
https://www.ibm.com/support/pages/how-configure-force-controller-use-tls-12
https://www.ibm.com/support/pages/error-occurred-while-trying-object-reference-not-set-repnetgetuserinfo-error-launching-controller-client-caused-tls-1011-disabled-ca-server