I'm not sure this is the right section, please let me know the new location of this thread if you decide to move it.
I tried to buy a Lesser Experience Elixir with this week Free Sample coupon. Unfortunately, I forgot my inventory was full. I got a message on screen telling me the purchase couldn't be completed since my inventory was full, and a second message telling me the coupon wasn't redeemed since the transaction didn't go through (elixir was not there, not even in "overflow bag").
I headed for a bank, emptied some slots in my inventory and tried to purchase the Elixir again. When I tried to complete the purchase, I got the red message telling me the code has already been used the maximum number of times. No free elixir for me, anywhere.
edit: I received the email confirming my purchase (even though the elixir was not delivered).
edit2: A couple relogs generated the elixir for me. I don't know why I didn't try the easiest solution first.