When using the "Express Checkout" option, you must enter your discount code in the discount field and click "Apply" prior to choosing the Express Checkout option if you want to see it reflected in your totals. We have recently changed the words on mobile to say "Have a discount code?^" instead of "Show order summary^"
Don't worry! You WILL have another chance to enter the discount after PayPal, GPay, etc returns you to the checkout page, and the discount will be removed from your total before final checkout.
If you've had troubles entering your discount code during checkout, please contact email@example.com as soon as possible. Thank you!