The most commonly-verifiable cause is that the business has switched this plan to Lock Menu mode: the meal-selection page shows a "Menu Locked" notice ("The meals for this plan are curated and cannot be changed") and meals are chosen for you automatically instead of something you pick. In the current version it's also plausible for a delivery date's ordering window to already be closed, or for your Diet Preferences/Allergens on My Profile to be filtering out every available meal — check those on My Profile first, then contact the business if meals still won't show.