cannot Install or update 2020 deluxe on Mac desktop
Why not? What is stopping you?
Does your Mac have the minimum system requirements for the TurobTax 2020 software - https://ttlc.intuit.com/community/system-requirements/help/minimum-system-requirements-for-turbotax-...
Do you have administrator rights - https://ttlc.intuit.com/community/troubleshooting/help/administrator-rights-mac/00/25636
Mac installation troubleshooter - https://ttlc.intuit.com/community/installing/help/turbotax-for-the-mac-installation-troubleshooter/0...
Contact TurboTax support for further assistance - https://support.turbotax.intuit.com/contact/