This error is commonly referred as “multiple matching error” and occurs when your Product ID (UPC, EAN, JAN, ISBN, etc.) is currently associated with two or more ASINs, but the other attributes you have provided in your inventory template (title, brand, color, size, etc.) do not match with any of these ASINs.
The provided SKU [SKU], conflicts with the Amazon catalog. The Standard Product ID value(s) provided for this SKU corresponds to the ASIN [ASIN]; however, some information is in conflict with the Amazon catalog. Following are conflicting attribute value(s): Item Package Quantity (Merchant: [Merchant Value] / Amazon: [Amazon Value]) or Part Number (Merchant: [Merchant Value]/ Amazon: [Amazon Value]). If your product is this ASIN, modify these attributes to reflect Amazon catalog values. If your product is different from this ASIN, check if the Standard Product ID value(s) are correct.
If the information in the Amazon catalog for this product appears to be incorrect, contact Selling Partner Support.