Error Code 5161
This error is caused if you add a trademark to your keywords. As Amazon does not allow this, you will not be able to create your item.
Solution:
Remove trademarks from your search terms in StoreAutomator. To do that, click Edit Product and go to the Tags tab. You can “Override” the bullet points search terms without changing the inventory data. After you override, click to Save&Close, then send a product data update and save the channel from the top right.