Error: SKUs do not match for ManageBySKU item specified by ItemID

When I try to update new SKU to ebay through API ReviseFixedPriceItemResponse, it returns

<span>"Errors"</span>: {<span>"ShortMessage"</span>: <span>"SKU Mismatch"</span>, <span>"LongMessage"</span>: <span>"SKUs do not match for ManageBySKU item specified by ItemID"</span>, <span>"ErrorCode"</span>: <span>"21916269"</span>, <span>"SeverityCode"</span>: <span>"Error"</span>, <span>"ErrorClassification"</span>: <span>"RequestError"</span>}

So what should I do to fix?
Anyone has ideas?