Since your 2020 return has not yet been fully processed then your 2020 AGI is not in the system for the IRS to use to match you up with that number. So, yes, in order to e-file 2021 you need to try using "zero" instead. You do not say if you have been filing late in the filing season for some of those past years-----if so, then you might be filing so late that the IRS has not put your previous AGI into the system and cannot match it up.
As for the state e-filing fees with the CD/download, you must talk with customer support. Only customer support can help with billing issues.
To call TurboTax customer support
https://ttlc.intuit.com/questions/1899263-what-is-the-turbotax-phone-number
Customer support is available from 5 a.m. to 5 p.m. Pacific time daily
No one in the user forum can resolve a billing issue. If you have a question about your TurboTax fees or billing, make sure you use the word “billing” in your request for help. Do not use the word “refund.”
**Disclaimer: Every effort has been made to offer the most correct information possible. The poster disclaims any legal responsibility for the accuracy of the information that is contained in this post.**
