I installed TT 2021 on an older Mac with an old OS that can't be upgraded. I tried to reinstall on a new Mac but I can't reuse the license code and I can't talk to a human on the TT side.
Use this website to contact TurboTax support during business hours - https://support.turbotax.intuit.com/contact/
Or -
Support can also be reached by messaging them on these pages https://www.facebook.com/turbotax/ and https://twitter.com/TeamTurboTax
Use this phone number and select TurboTax - 1-800-4-INTUIT (1-800-446-8848)
On every TurboTax web page, including this one, scroll down to the bottom of the page and click on Contact Us
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