Andrew,
I just tried it and the discount code worked. (I tried it in upper case and lower case, both worked. The code is not case sensitive.)
Try it again. If it doesn’t work, it may be because Banggood has mistakenly identified you as a dealer. Banggood’s ordering system seems to randomly do that to people. You can contact Customer Service and have them fix your status or you can re-register under a different party.
EDIT: Additional reference information.
Take a look at post nos. 4146 thru 4152: BLF Kronos X6/X5 GB - Group Buy now closed.
See also post nos. 259 and 260: 30Q button top - new deal for Q8