Have you already filed your tax return? You won't be able to downgrade if you already filed. Your tax situation may require the upgraded version. You can downgrade your current TurboTax version with our clear and start over feature but you won't be able to use this if you've already filed, registered, submitted payment or deducted the TurboTax fee from your refund.
Please see this TurboTax FAQ for more information:
https://ttlc.intuit.com/community/downgrading/help/can-i-downgrade-to-a-lower-priced-version-of-turbotax-online/00/25591