It is likely you are using an output style that has not incorporated the “Cited Pages” field in the citation template. Two solutions.
One: Edit citation and type the pages and any associated text, spaces and punctuation into the suffix field instead of in the cited pages filed.
Two: modify the output style - edit the output style Citation Template you are using and you will want the template to look something like this:
(Author,*|Year|,*p.^pp.*Cited Pages|)
Where the asterisk should be replaced by the “link adjacent” character from the “insert field” dropdown menu.
Then SAVE AS (very important) give a slightly different name (to distinguish it for yourself) and then make sure to change the output style you are using in your manuscript to the newly named output style. You may have to first “select another style” in word in the endnote ribbon if it isn’t yet showing in the list.