If you have purchased a prepaid activation and not used that code already, you should be able to use that code on the payment page of TurboTax Online. This, of course, will not work if you have already entered a different activation code on that same return.
If you do have an issue with your Prepayment/Activation code for a TurboTax Online product, please reach out to us directly as we cannot exchange personal information in this public forum.
You can reach out to us via private message on one of our social network channels. Facebook/Messenger Private Message or Twitter Direct Message
You can also contact our Support Team by following the link below and in the field that says "Ask your question", type in "your question" and you will be directed to an agent that can assist you. TurboTax Customer Support