How do I get Mac software to file an amended 2016 return ? Mac was available to amend my 2017 return by 2016 only has windows software.

See this TurboTax support FAQ for requesting 2016 Mac software so that you can amend the 2016 tax return originally completed using the online editions - https://ttlc.intuit.com/community/amending/help/how-to-amend-change-or-correct-a-return-you-already-filed/00/25588

@DoninGA @Thanks!