I am getting "page not found" on pages other than my

I am getting “page not found” on pages other than my “store” page (eg… products, shopping cart) although the items still appear, I’m getting that message. I left the structure as default. I am also using “membership” and “events+”. I was told I did not need to create pages for the slugs related to the store, is that correct? If so, why am I getting “page not found” errors?