Meta
A Page admin signs in with Facebook Login. Meta returns only Pages they administer. That is how NajedCare verifies a subscribed customer before operating Messenger or Instagram for them.
Checking the Meta app…
No Facebook Pages are verified for Lumen Atelier yet. After a Page admin finishes Facebook Login, they appear here with their Instagram professional account if one is linked.
Standard Access only works for people with a role on the app. For live subscribed customers you still submit App Review for Advanced Access, finish Business Verification, and complete Access Verification as a Tech Provider. Those clicks happen in Meta Business Manager — NajedCare cannot submit them for you.