I went ahead and setup Amazon FBA with Shipstation in order to do multi-channel fulfillment.
One of the main reasons is that once in a while, a product sold on Amazon with Prime can be taken out for review by Amazon if the return rates are too high. When that happens, I usually create an FBM offer on the same SKU, so that I in that way can keep selling it as FBM until the review by Amazon is over.
The Shipstation and FBA integration allows me to keep using FBA to send those orders, even though they are bought as FBM. However, in doing so I noticed 2 things.
1. The ORDER ID changed when I send the order to FBA from Shipstation. Amazon created the shipment, but didn't recognize it under the original FBM order ID. Instead a new ORDER ID was created.
2. The orders in Amazon remained unconfirmed though it had been shipped. Now I have to copy paste the tracking ID from Amazon into Amazon. It seems odd that it doesn't submit the tracking number automatically?
3. The orders stay in Pending Fulfillment Status in ShipStation, even when Amazon has shipped the item.
I have a feeling all of this could be fixed if Shipstation fed the correct Order ID into Amazon when creating the shipments, but I am not sure. Maybe there is a simple explanation to all of it.