user can not use their Gift Certificate on cart

one of my user, can not use his Gift Certificate balance to buy product.

after submitting coupon in user balance page, the order is not submitting... and balance is not change.

joomla 3.7.5

virtuemart 3.2.4

awocoupon 2.5.9.1

i will post the test environment to you in private

Thanks for the access.  After testing it, seems to be working.

thank you, seems ok now