You must also set Store ID and/or Category ID. First set your Source ID and save the module settings. After that, you will see links for finding Store ID and Category ID:
After migrating from Lomadee API v2 to Lomadee API v3 (Content Egg 6.0.0), they changed the product IDs in the database. So it is not possible to track prices and stock status for already added products (with API v2).