It may be because your Internet browser is removing the cookie information that was stored in previous account access sessions. And, if you marked your computer as "private," this information is also removed. Most browsers have an option to remove web site cookies each time the browser is closed. If you would like to disable the automatic removal of cookies so that you are not presented with the enhanced login security each time you log into online account access, please visit the Help menu for your browser.
After you have changed your settings, you may need to close the browser and re-open it before logging into online account access. You will then need to register your computer as private to skip the enhanced login security each time you login.