M2E Pro extension must be granted a user token to be able to interact with eBay. The user token authorizes M2E Pro to access eBay data on behalf of an eBay User. A user grants an application a user token by giving consent via the eBay sign-in and consent page.
The Extension allows granting and using an unlimited number of user tokens for eBay accounts, which operate in the Production or the Sandbox environment.
M2E Pro requires at least one eBay account set for interaction with eBay.