I have a small Site that has been deployed for a year or so with read/write access to a single custom object. I recently added a new field to the object and one of the VF pages, and modified the behavior of the page to be more responsive. I granted access to the field to the Guest User profile and the page works fine from apex/pageName when I do my initial testing.
Visitors are directed to the site via email/sms links that we send out.
The updated page is not the initial landing page [InventoryPortalWelcome, as indicated below]; I do some validation of the URL parameters first, and if they're in good order the visitor is redirected to the updated page. When I test the email links from the sandbox, however, the site displays the 'Under Construction' page instead. The Site page (screenshot) below is from the sandbox.
Where do I look to determine what's preventing the updated Site from performing/appearing correctly?