Be sure to read through the Terms & Conditions to make sure the product you purchased is identical to the one in the app and eligible for cashback. This includes the product variety, size, flavor and other specifications listed in the Terms & Conditions.
Please "check product eligibility" of the offer by clicking on the piggybank icon on the bottom of the app. That way, you will make sure you get the right product before you actually purchase it. 
You can also check that the barcode numbers indicated by the app are the same as the product, if not it means that the scan didn't work properly so you can try again.
Depending on the barcode position in the product, you may have to try a couple of times. 
- Make sure that the packaging is not wrinkled or deformed.
- Double check that you have authorised Shopmium to access your camera.
- Verify that your smartphone has autofocus because it is mandatory to be able to scan a barcode.
- Make sure that you have the latest version of the app on your device (Try restarting the app or log out and back in)
If that still doesn't work and if you believe your product is mistakenly being rejected, please contact us and send us a full picture of the product (front + back with the barcode).