After the successful installation of the Vendor eBay Product Importer addon, an admin needs to enable the service for the vendors.

To enable the extension admin need to login to a website admin panel and navigate to the store configuration

Magento Admin Panel < Stores < Configuration < Marketplace < Vendor Configuration

At this point in the section, you need to move to the GENERAL section where an admin will have the option for all the installed extension to enable or disable the feature.

After enabling the feature for the vendor, now vendor will able to check the eBay Product Importer option in the menu tab on his vendor panel.