Answer
Permission-set access alone doesn't guarantee visibility — walk through a short checklist: confirm the new page has actually been enabled/made visible in the user's Profile (a page can be fully permitted but still hidden at the profile level); refresh both the Security cache and the Dictionary cache, since a stale cache can artificially block a newly added page from appearing for a period of time; and clear the local cache on the user's own machine as well, since client-side caching can also mask a recent server-side change. If none of that resolves it, swapping the user's profile (or permissions) with another user who can already see the page, one setting at a time, is a practical last resort for isolating exactly what's blocking visibility.