It can take up to 24 hours to import all existing 3rd party listings, depending on the size of your Channel inventory

Only 3rd party Items which are not older than 4 years will be imported.

Note, M2E Pro 3rd party Import Tool does not contain the functionality of importing the eBay Category data. The Category settings have to be provided for the products in M2E Pro Listings after the 3rd party items are moved.

We highly recommend you to map identical products: imported Simple Product with your Magento Simple Product, and Variational Product to Magento Variational Product with the relevant variational attributes and options. It allows avoiding the system confusion when applying actions (e.g. Revise, Relist) and order creation in M2E Pro