It might be that not all the forms in your return have been finalized yet. If you have Draft forms in your return, it would not allow you to finish your return.
Use this link to reference when your tax forms will be available. You can search by TurboTax Product and for IRS and State-Specific Forms.
montana tax laws were substantially changed requiring substantial changes to the income tax form. while the state has finalized it, Tirbotax says it won't be available until 1/30/2025.
you can still e-file your federal return. Turbotax suggests deleting the state and coming back to redo it later. Not sure that's necessary. what I've done in the past. select mailing for the state and then later come back and switch the state back to e-file.
from TurboTax website