Updates and amendments of warranty is not allowed as it may create conflict with past sales. Please create a new SKU with updated warranty.
SKU's warranty is being updated to a different value from the current. Take note that changes in the warranty information of a product should increase its market value.
Amendments of product specification is not allowed into the existing value. Warranty amendment is only permittable if it is correct or being added for the first time for the product. You may create a new SKU with the updated warranty and deactivate your existing SKU.
Warranty information can be changed when managing your products (Step 4 of product creation/management). However, keep in mind that it SHOULD NOT DEVALUE the current SKU's warranty.