You will need to submit a Missing Cashback request for every order that's missing.
Here's where you can do it ("Report a Missing Cashback"):
1) On the mobile app, click on the user icon beside the notification bell and search for "Report Missing Cashback".
2) On the website, click on "Cashback Overview" and you will see a red button for "Report Missing Cashback".
3) Click here to submit the 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 merchant. The investigation will take around 14 days to be completed(Investigation for Expedia Australia missing cashback request will be completed 75 days after checkout/travel).