To add a disconnected marketplace again to your SelluSeller account, sign in to SelluSeller, click in the upper-right corner on any page, and then click Configurations. The Configurations page appears with the Fulfillment Management tab by default.
Click Marketplace Management and in the Action column, click Connect for the marketplace that you want to add again. The Connect Marketplace pop-up window appears.
In the Connect Marketplace pop-up window, enter the API Key and Contact Email and then click CONNECT. The respective marketplace is immediately added to your SelluSeller account.