Had the same problem, caught in a loop where TurboTax Business wouldn't let me purchase the state. Never could get to the point where it would take my billing information.
While talking with tech support (who admitted they were unfamiliar with TurboTax Business and never did help me) I started looking around TurboTax Business -- I found something that helps.
On the top ribbon there is "Help". Then under that there is a selection for "Pay by Phone" and then a further selection of "Additional State" Select this. This will pop up a screen regarding "Purchase by Phone" with instructions.
1) This will direct you to "Call Intuit Sales and Services" at .....
2) It will give you a serial number that you have to give them.
3) Once they charge your credit card within your Intuit account they will give you a "State Product Confirmation Number" You input the confirmation number, hit "Continue" and it will download the state software.
All sounds pretty simple, and should be, but not with Intuit.
As a warning, this did not go very smoothly for me, and it took about 80 minutes for them to process the order for two states that I needed to download. And they accidently charged me twice for one -- said they are reversing, but I will need to check that in a few days. They also had problems with my first credit card, so I had to add a second credit card to my Intuit account. I think their system was messing something up.
But at least I now have the two additional states that I need. Never had to work so hard to pay a business for add ons.
If you are downloading more than one state my advice is to download states one at a time. So first go through the process for one state. Then after it downloads let them know that you would like to do the same for a second state. They are able to set up an order for multiple states at one time but there is no way for you to input the confirmation number for more than one state. So only tell them about one state at a time.
