Can't I buy humble tell tale making bundle twice?

Humble has algorithms in place that are designed to thwart fraud and resellers. If you try to buy multiple copies of something or make more than a couple of transactions in a day, you will be blocked. In the case of the Telltale build-a-bundle, it's probably intended to limit it to one bundle per person. The only way around it is to:

(1) Delete all your browser cookies.
(2) Restart your ISP's modem so that you are issued a new dynamic IP address (those with a static address are in trouble).
(3) Use a different payment method. If you used Paypal yesterday, try using Amazon Payments or a Credit Card today.

I have bought it three times today.

Yes