Do you get an error message?  How far do you get?  Do you see the download in your account or can't you find the right account?

Does your Mac have the System Requirements?

https://ttlc.intuit.com/community/system-requirements/help/minimum-system-requirements-for-turbotax-...

A Mac user posted these.  Maybe they will help.
https://ttlc.intuit.com/questions/2899293-turbotax-for-mac-won-t-open-when-installed

https://ttlc.intuit.com/questions/1899267-administrator-rights-mac

https://support.apple.com/en-us/HT202491

The only options available for download are for Windows. Windows uses .exe files. These do not work on Macs.  I have the same issue as the OP. I need to download the TurboTax Desktop 2018 to amend my 2018 return, but there is no option for Mac users.

The MAC version of TurboTax Desktop is available for 2016 - 2018.  To purchase and download, go to: File your 2018 taxes.  When you click on a version, you will see a pop-up window asking you to choose PC or MAC.

I've already paid for my tax return. I need to amend it. Should I have to pay for it again? The download is available for PC but not for Mac.

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@VikkiB wrote:

I've already paid for my tax return. I need to amend it. Should I have to pay for it again? The download is available for PC but not for Mac.

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If you used the TurboTax online editions to complete and file the 2018 tax return, then you can amend the 2018 tax return using the online editions, no need to download the amend software.

See this TurboTax support FAQ for amending a 2018 tax return using the online editions - https://ttlc.intuit.com/community/tax-topics/help/how-do-i-amend-my-2018-turbotax-online-return/01/9...