If you are seeing two accounts, both with Listing Sync Pro (not through Yext), but one has fewer listing sources as compared to the other one, this may be due to one being marked as a Service Area Business, or another reason that the business information is not accepted by a source, such as business category.
The Listing Sync Pro product does not display any listing sources that may not be applicable to a specific business. Yext will display all potential sources whether they can be synced to or not.