/%Postname%/ permalink = 404 File not Found….WHY?

Hello. I am trying to set the permalink under common settings to just /%postname%/. When I save the settings and return to visit my site, all of the links I click on then have a 404 File Not Found error message. Why is this happening? Is am usuing a static page for the front page. I can provide more info is needed to diagnose.

I am building a wordpress based info page for my parents’ shop. Thanks for the help!