Problem

I am using JIRA Data Center / Server. I checked the "Enable SSO Redirect" in the plugin configuration. I tried to access my JIRA main URL https://<jira-URL>, /login.jsp, /default.jsp, /secure/Dashboard.jspa and /secure/MyJiraHome.jspa but I always end up on the normal login page.

Solution

The "Enable SSO Redirect" is working with the "Force SSO URLs" field. That means that the SAML SSO app for Atlassian Data Center or Server is only redirecting requests to URLs matching the regular expressions from the Force SSO URLs. To ensure that your main and all normal login URLs will be redirected, please check if the "Force SSO URLs" has included the default values: 

/

/default\.jsp\??.*

/secure/Dashboard\.jspa\??.*

/secure/MyJiraHome\.jspa\??.*

/plugins/servlet/mobile.*

You also can delete all entries in the "Force SSO URLs" section and use the "Restore default" link below it to restore default settings.
Don't forget to save the configuration.