It could be those sales didn't qualify for eBay automated feedback. The help file (for buyers) states:
eBay automated feedback is automatically added to the seller’s account when a transaction is successfully completed. This positive feedback gives other eBay users confidence in this seller and in our marketplace. We only do this if the following criteria are met:
- You didn't leave feedback within 7 days of delivery (as confirmed by tracking)
- We can’t see any indication of an issue with the transaction
- Tracking shows the item was delivered on time
Automated feedback from eBay will remain visible unless there is an indication that there was an issue with the transaction, for example the item was damaged or you opened a return. If this happens, we will remove the automated message.
You can still leave your own feedback within 60 days of delivery, in which case the automated feedback will be replaced with yours.