CashKarma uses the device ID (IDFA) to track rewards, provide more rewarded offers, and for fraud prevention purposes. 
TO ENABLE:  Go to Settings > Privacy > Tracking and enable cashKarma (Allow Apps to Request to Track needs to be enabled)
HELP! I DON'T SEE "Allow Tracking
Go to Settings > Privacy > Tracking  and enable  Allow Apps to Request to Track. Then re-open cashKarma and follow the steps once more.