MS Office not working after upgrading to Catalina

If you have Office 2011, it's 32-bit and it won't work on Catalina. You can either buy Office 2019, subscribe to Office 365 or try the free Office Libre for Mac. It works fine with Office-files

https://www.libreoffice.org/download/download/?type=mac-x86_64&version=6.3.3&lang=en-US

You could also see if Apple's apps Pages, Numbers and Keynotes suit your needs

Download Microsoft Office 2019 OR update it to Microsoft Office 2019.

Older versions are not compatible with Mac OS Catalina.