If you are seeing this when you have bought Zen off Cryptic there is a way around it.
After buying Zen you may then purchase some keys to sell which are bound to account for 7 days. To combat this ludicrous issue, and we don't know if it's by accident or design, do the following.
Go to the Zen store, purchase 20 infinity boxes, these are free.
You can now purchase the keys and they will no longer be account bound.