Promo code tab doesn’t work – Caviar - Order Food Delivery Review

I can’t even enter a promo code because the app closes the page when you click enter promo code. I would have spent $20 and used the code IMBACK15 that was emailed to me, but I could not enter the code because of a flaw on the app. My app is up to date on updates in the App Store. 1 star review bc the app doesn’t work - send new promo codes please
Review by hungry farah on Caviar - Order Food Delivery.