page doesnt show …sometimes version 4.4.1

had to reinstall wp. all seems to be well except page not found errors.
the homepage always works! that seems odd.

if I make a new page it looks good in preview when I click publish it is the error page

other posts on this are way years old so trying a new post.

should I try once again to reinstall? import a backup? sorry no degree in php code writing to fix things that way.