After you enable an eBay seller account in Monsoon Marketplace, you should never list items outside of Monsoon Marketplace using the same eBay seller account.
If you list items directly on eBay using the same seller account that's enabled in Monsoon Marketplace, your Monsoon Marketplace inventory won't synchronize with your eBay listings.
To keep your inventory synchronized, use a different eBay seller account to list any items outside of Monsoon Marketplace.
eBay Listing Synchronization overview