How do I configure the syslog to send message when user logon to the router, either success or fail.
Do you have the pre-requisite "login block-for seconds attempts tries within seconds" configured, as specified in this section? I'm not sure how "log on-success ..." worked if the above were not configured.
Also, according to this document
"Logging messages for failed login attempts are automatically enabled when the auto secure command is issued; they are not automatically enabled for successful login attempts via autosecure."
You'd need a certain version of IOS deployed. Details in this thread: