Hi - we've had a lot of feedback with people having difficulty finding where to add the coupon code. On a desktop it's much clearer (to the right of the screen), but on a phone it's all the way at the bottom - so unless you scroll further they seem to miss it and abort the order.
If it can be moved to under the 'Your Price' section of the Billing screen that would help avoid a lot of these support tickets.
Thanks for listening!