How to Set-up Page Permalink w/Parents

Trying to set-up links in a parent page to respective sub-pages. Permalink listed in subpages doesn’t work – I Get an error:
Whoops! That Page Isn’t Here
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Have tried permalink settings:
Custom Structure /%category%/%postname%/ AND /%postname%/

Problem is the permalink is for a “page” not a post” – I searched WP structure tags but found nothing for “pages”

will appreciate any help you can give. Thanks akt