Error 500 when trying to redeem a code for a pre-order

I have a code for the standard pre-order for the showdown expansion which I was going to share with a friend, but when I tried to redeem it to see if it works I get an Error 500 message with the error code: BLZWEBBM(random last part). I also asked another friend of mine who doesnt play hearthstone to redeem the code and he got the same error.
I already contacted the support. They confirmed that the code is perfectly working and suggested that I open a thread here and report the bug.
Maybe one of you experienced the same bug and knows how to fix it.

What do you mean you were going to a share a code ?
Codes are one-use only

its an unused code. I wanted them to have it