Download Listings option saves listing information in the database. Clicking this button forces Linnworks to request an update from the channel for all your active listings.
Settings > Channel Integration > Edit channel details > Listings
For eBay, Download Listings additionally to above also triggers the inventory check. Linnworks will compare current stock levels in the system to what was lastly sent and if there will be any difference it will send new details to the channel. For this reason, a limit is added to eBay – Download Listings can be clicked once every 12 hours.