You will need to submit a Missing Cashback request for every order that's missing.
Here's where you can do it:
1) On the mobile app, click on the user icon
2) Search for "Report Missing Cashback" and select ShopBack GO transaction
3) Click on Purchase Details to submit your Missing Cashback request
IMPORTANT: Missing Cashback submissions must be within 30 days from the purchase date. Any submissions past the specified time are invalid and will not be investigated by the network.