Need to add the 2020 Massachusetts state tax return to my downloaded 2020 TurboTax?

Sorry--TurboTax no longer supports or provides updates or state downloads for 2020 software.   If you need to prepare a 2020 state return, you might be able to obtain the forms from the state to prepare by hand.  It is too late to get a refund for a 2020 tax return.

https://ttlc.intuit.com/turbotax-support/en-us/help-article/state-taxes/contact-state-department-revenue/L9qVToi02_US_en_US?uid=m6e06um0