Sale price effective date must be a slash-separated start/end ISO 8601 date pair (e.g., 2026-04-05T08:00-08:00/2026-04-10T19:30-08:00).
Microsoft Merchant Center'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.