Aliexpress Coupons

Hi, your extension is awesome I tried to write a simple one like yours which is inputting a coupon code of my choice in the coupon input on Aliexpress at checkout: But the problem is that the text (coupon code) disappears and even if it stays, when I press apply button, nothing happens, and when I check the element in question, there is no value there, although it displays.I couldn't figure out how did you do it.