how do you guys use the lazada (android) app?

when i check out, i select maybank, then add on the voucher, got the voucher verified and accepted. at the last part, all i get is the [processing] , [cancel] selection with the timer. that's all. it doesn't route me to the maybank2u.
after the timer ends, i'm stuck with the circling lazada logo with a blank white background.

what's wrong?

i'm tired of using the mobile app. i use it for the sake of the lunar100 code to buy a redmi note3.
is it possible for me to checkout on a desktop with that voucher applied? if not possible, could you please suggest a non-app voucher.