CAT_VALIDATION_EXPIRATION_DATE_INVALID indicates expiration_date is not a valid ISO 8601 timestamp or sits in the past. Expired items are dropped from active product sets at the next refresh.
Snap Catalog Manager's product schema has format and value rules per attribute. This issue is typically: missing a required attribute for the category, an invalid enum value (e.g., 'XL' submitted where 'M, L, XL' is the valid set), out-of-range numbers, or attributes that conflict across the feed.