I’ve created a user role a few years ago with permissions to create pages (not publish) and to edit pages created by the same account. All plugins have always been kept updated. Suddenly the option to create a page or edit a page has just stopped working.
Confirm that required capabilities (create_pages, edit_pages, publish_pages, edit_published_pages) are still granted to this user. If Yes, try to deactivate all plugins. If it will return ability to work with pages, activate plugins back one by one to isolate a reason.