Amazon: not possible to submit feeds (products), but can receive orders
In some cases, Amazon may reject product submissions, even though the Listing Status in your Seller Account Information is set to 'Active' and it's a professional account.
If ChannelEngine is successfully added as a third-party application with valid MWS credentials (this can be tested by calling the /orders endpoint), normally all operations like retrieving orders and submitting products can be performed. However, if we receive below response from Amazon, we are not able to create new offers / products on Amazon
<Code>InvalidMarketplace</Code> <Message>Feed rejected</Message>
If this is the case, please double-check your payment information in Seller Central including the credit card information (if applicable). You can get there via 'Settings' > 'Account Info' > 'Payment Information'. If approved / updated, you will receive a mail from Amazon after which it should be possible to submit feeds (again).