This error normally appears when there are forms in your return that are not ready for e-filing.  You might try restarting the review and then filing steps and take note of any messages about forms not ready. Please see the information here for assistance with this formset error.

Try this:

Delete the state portion, and then add the state back. Continue to fill out the state return, do a review with the federal and then proceed to register the state. 

We have received numerous reports of this experience that appear to be coming from various areas of the program. Please troubleshoot with the options below. If needed, we will need to investigate your experience.  Thank you for your participation and patience. 

A. Check Availability

Please confirm all forms you are filing are available and supported to be e-filed. When will my forms be ready?

(The 8915-E Form is projected to be e-fileable starting 02/24/2021)

B. Remove state and try again
 If all your forms are ready and available to be e-filed and you receive this message, please follow the steps below:

1. Sign out of TurboTax.
2. Sign back in.
3. E-file the return again.

You may need to remove your state and prepare your state return again to move past the error and successfully e-file.

C. Send us your tax file
Still, receiving the message? We'd like to take a deeper look at your specific situation. Please attach screenshots, detailed instructions on where you are in the TurboTax Program, and a token number. (This token number gives us your tax file with all your personal information removed)

TurboTax Online:  
Click Tax Tools in the menu to the left.
Click Tools, and then
Click Share my file with Agent.
A pop-up message will appear. Click OK to send the sanitized diagnostic copy to us.
Provide the token number that is generated onto this thread.

TurboTax Desktop:
Select Online menu if you are using Windows. Select “Help” if using a Mac.
Select Send Tax File to Agent.
A pop-up message will appear, and the customer will select, Send. If using Mac "Send Tax File to TurboTax Agent" 

Note: Desktop will save a file to your computer unless you uncheck the box.
Another message will appear. Provide the token number that is generated onto this thread.