Microsoft

Depending on the version of Office that you had, it may not be compatible with Catalina.

If you have an early version of Office for Mac 2016, you can update it at no charge. See: https://docs.microsoft.com/en-us/office365/troubleshoot/administration/office-2016-for-mac-64-bit-upgrade

If you have Office for Mac 2011 or earlier, you can either subscribe to Office 365 or you can make a one-time purchase. See: https://products.office.com/en-us/buy/compare-microsoft-office-products-for-mac?ms.officeurl=mac-compare-redir

Or the free Microsoft Office on the web: https://products.office.com/en-us/free-office-online-for-the-web

Or Google Docs: https://www.google.com/docs/about/

Other options include using the free and very good Libre Office https://www.libreoffice.org/

or Apple's Pages and Numbers

The why is that Office 2008/2011 are 32-bit Office suites, and Catalina only supports 64-bit applications. Office 2016 after Aug 2016, current Office 365, and the single-purchase Office 2019 for Mac are all 64-bit solutions, and will open your earlier Office suite files which are not affected by the 32/64-bit issue.

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