Just installed macOS Catalina and now cannot use Microsoft Word, Powerpoint or Excel.

Older versions of Office are not compatible with Catalina.

If you have an early version of Office for Mac 2016, you can update it at no charge. However note that connecting to Microsoft 365 services using Office 2016 for Mac is not supported by Microsoft after October 13, 2020. 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 Microsoft 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 use 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

It would seem that your prior purchase was for an older 32 bit version of Office. Catalina now requires that only 64 bit apps be installed. Apple has regularly informed all of us for a couple of years that at some point our old 32 bit programs would no longer work with a future OS upgrade. The key question is which version of office do you have. If you have Microsoft Office for Mac 2016 or later, it can be updated at no cost. If it is an earlier version, it cannot be updated and you will be charged for an upgrade.

I hope the following is helpful to you in addressing ‘problems’ with Microsoft Office after an OS upgrade to Catalina.

·      Any other old 32 bit programs you have installed will also be affected. They also will no longer work and will have to be upgraded or replaced.   

·      If you elect not to upgrade Microsoft Office, there are excellent alternatives. They are the free LibreOffice and OpenOffice apps. Additionally, your Apple OS provides three free programs which you may use as an alternative to Office, Pages, Numbers and Keynote.

·      Any of these apps can and will open your older Office documents, allowing you to work with them. With them you may also create new documents and save them as Word files, etc. when you need to share files with other people who only have Office installed.

·      You should be aware that using these other apps to open Word documents will likely result in formatting changes.

·      Using any of these programs does involve a learning curve as they work a bit differently, but all of them are fine programs and they are free.

·      If you decide to upgrade from an older version of Office, you have options. You may elect to subscribe to any of the following:

• • Office 365 Home:  $99.99 per year or $9.99 monthly. This allows you to install Office in up to six devices. This service must be renewed yearly. You may try the service free for one month.
  • Office Personal:             $69.99 per year or $6.99 monthly. This is for installation on one device only. This service must be renewed yearly. You may try the service free for one month.
  • Office Home & Student:  $149.99 one-time purchase cost. This is a purchase for installation on one device only and is not renewed or have a monthly fee. It does not expire.
  • The second and third options include fewer additional apps such as having no Outlook app. Check the Microsoft site for details.

·       Finally, and this is important, when purchasing any of these Office upgrades, you need to register your purchase on the Microsoft web site, including which device or devices the apps are installed on. This can be changed later if a device is replaced. You must do this registration or you can have problems.

In summary, Apple has warned us of the coming change to 64 bit operations only. It has occurred. Now, it is up to us to decide how to proceed. I hope this information is helpful to you. Good luck.