Does Apache user has read permission on SiteMinder webagent directories?
Start and stop Apache only by using apachectl.
If you are running 6QMR5 CR13 or older versions of webagent then make sure LLAWP is not running before Apache is started.
Make sure correct installer is used depending on32 bit or 64 bit WebServer.
Some OS Kernel setting needs to be tuned. Make sure that it has been done according to Web Agent Installation Guide > Operating System Tuning
If still failing then please provide CA_SiteMinder_Web_Agent_version_InstallLog.log, /opt/netegrity/install-info/nete-install-history.log and nete-wa-details.log when opening Support case, as well as webagent and webserver configuration files