We've had complaints about stock sync not functioning because of mistakes on Amazon's side after your account is opted into Remote Fulfillment with FBA.
"Error - An FBA offer already exists on this SKU. To create a seller fulfilled SKU, either create a new SKU or make the SwitchFulfillmentTo value MFN. (96016). Message ID: 197"
This appears to be caused by Amazon's new Remote Fulfillment with FBA offering which when you enable it mentions:
> Amazon Marketplace Web Service users: After enrolling in Remote Fulfillment with FBA, inventory updates using the Inventory.xsd feed will require the SwitchFulfillmentTo element to be populated with the fulfillment channel (AFN or MFN).
The user BigKitchen in this forum post explains a solution to the issue, including SwitchFulfillmentTo field with value MFN in the update feeds should resolve it.
Unfortunately, SKULabs listens to Amazon through the listings sync process for when your offers change and we only push inventory to MFN offers enabling us to provide a seamless solution for stock sync. SKULabs does not at this time override your listings when we push out stock levels. Amazon is known to "reconfigure" your offers when they modify your listings which could cause SKULabs to inadvertently convert the wrong offer to MFN if we did so.
At this time, we recommend you un-enroll your account from the Remote Fulfillment program.
We are current investigating how we can safely enable switching your fulfillment mode on offers without interfering with known changes made to offer configuration outside of SKULabs either by Amazon themselves when their automated reconfigurations occur or when your team changes an offer from AFN to MFN.
How to check if you are enrolled and unenroll
According to Amazon's documentation, below are the steps to enroll to the Remote Fulfillment program. In case you haven't done so, checkout the instructions below to review the enrollment status of your account and to unenroll from the Remote Fulfillment page on Seller Central:
"To enroll in Remote Fulfillment, you must be registered for FBA in the US, Canada, and Mexico and have a North America Unified Account with FBA Export enabled. Once you enroll, your eligible ASINs will be available for sale to customers in Canada and Mexico as soon as you create offers for them on Amazon.ca and Amazon.com.mx.
Follow these steps to enroll and begin selling:
1. Go to the Remote Fulfillment page, which you can also find using the Inventory drop-down menu on Seller Central.
2. Set your preferences as you go through the enrollment workflow, and click Enroll. [uncheck the Enroll option to unenroll] Once you have enrolled, Amazon will evaluate your inventory and automatically add all eligible items to the program. From then on, we will automatically add to the program:
Any new eligible item added to your US inventory
Any items that are currently ineligible but later become eligible
3. If you haven’t enabled automatic listing creation in your setting preferences, create offers for Canada and Mexico so you can sell your US inventory in those marketplaces.
4. Download your ASIN Status report from the Remote Fulfillment page to:
See which of your ASINs have been added to the program
Find out if you have to take action on any ASINs so they can be added to the program
Remove ASINs from the program that you don’t want to sell in a particular marketplace"