Got my Voucher today.
I have now received the code too. 
Just had to prod them I guess. 
Hm, tried to use it and it says “This code is not available to you right now” Hmmm how to use the voucher then. 
Got my code also, so an answer to your question about how to use it would be helpful.
I had to sign in again for it to work, seems linked to the email. I opened an incognito window, went to the snapmaker store, added the dryer, then signed in, and then it accepted the code in the promo code area during checkout.
Thanks
Mark
Got to smile; I had to pay $10 shipping.
Mark
That’s the price of free. 
I had to pay € 12,-- shipping 