All errors are cleared by clicking the "Acknowledge" button. The button is located on the item's panel that you can find by searching for the item or locating it through the Inventory menu. After clicking "Acknowledge" the item is reset and ready to sync again. This takes about 2 minutes, during which time we double check you seller accounts to verify the item's status.
If the error has no message, then when syncing you likely entered an incorrect or non-existant ASIN in the ASIN field. Be sure to use the ASIN search button and locate your ASIN in Amazon's product catalog. The ASIN (Amazon Standard Identification Number) is very important. It tells Amazon where to place your product. A UPC or other number will not work
If the error has a detailed message, it is Amazon responding to tell you why it cannot post your item. Most of these are for product permissions. Amazon has a few items that require explicit permission to post. If you run into one of them you can go to your account and file for permission to list it. They do this for toy sellers around the holidays, and for anything with "Certified Refurbished" in the title (among other things). It's Amazon's way of guaranteeing the quality of important product deliveries. (like kid's presents around the holidays)
You can review detail information about categories with restrictions and requirements here: https://services.amazon.com/services/soa-approval-category.htm/ref=asus_soa_snav_cat_t1
If all items come back as errors when synced. We are still working on implementing Amazon.ca (Canada) if you have an Amazon account based in Canada and your items are not syncing please email firstname.lastname@example.org and we'll try and update your account.