In another thread, a number of users have addressed their experiences with this formset issue. The main solution was to delete the state and re-add it (look for GabiU's comment at this TurboTax Community thread on page 2).
However, several of the users who were asked to pay for the state when they re-added the state, found out that they had only paid for the federal return and not the state, that is, when TurboTax asked them to pay, TurboTax only charged for the federal return, not the state.
When the taxpayers paid for the state, then they were able to add it and the e-file went through just fine. See this TurboTax Community thread (3 pages).
I don't know what you have paid, but you can see what you owe by opening your tax return (I assume you are using the Online product). On the left, click on Tax Tools, then underneath it click on Tools. In the center, then click on the blue-green box that says "My Fees".
If you paid, say, $40 previously, this probably was only for the federal return, and another $40 is due for the state.
I do not know why TurboTax apparently charged some taxpayers only for the federal return and not the federal and state, but deleting the state, re-adding it and paying for the state, allowed them to file the return with a problem.
Let us know if this works for you.