I found there might be a bug there, here is how to replicate the issue:
1. Enter coupon code & apply. (Total price has change)
2. Checkout to PayPal. (My site use PayPal for payment only)
3. The price shows in PayPal is perfectly discounted.
4. Click "cancel and back to site" in PayPal page.
5. Back to cart page, every info remain the same, the total price in the cart still shows discounted price.
6. Click checkout to PayPal again.
7. The price shows in PayPal is the original price and not discounted, customers will have to pay the full price.
However, if I enter & apply the coupon code again at step 5, although there seems nothing change, it would show the right discounted price when moving forward to PayPal.
AwoCoupon Pro v188.8.131.52
RuposTel One page checkout v2.0.348
Thank you for your support.