SAP Netweaver Portal

Steps to identify and resolve the issue:
• Check the Keystore administrator in Visual Admin to determine the valid date and from date and these dates should be in the future and not expired.



• The dates for SSO will be the same in the application (system administration > system config >key store admin) as shown above; in the OS (Visual Admin) and in ECC (tcode: STRUSTSSO2). The OS generates a self signed certificate and this is stored in the application in the keystore area. This is exported and imported to ECC in tcode: STRUSTSSO2.






• Check tcode STRUSTSSO2 in the system which has to be single signed on and determine under the certificate area the valid from and valid to dates and make sure they are in the future as shown above.
• If the certificate dates are old follow instructions in the below link to create a new certificate:

http://wiki.sdn.sap.com/wiki/display/EP/SSO+Certificate+Expiry

Also check to make sure the connection tests for the system object is successful and refresh the system object after the new certificate has been created


References:
http://help.sap.com/saphelp_nwes70/helpdata/EN/2c/f4e76d7f9e4ffbbc0bfbc0c16fe49d/content.htm