Big Sur 11.2.3 | Issues opening Office365 Applications

Microsoft does not provide free upgrades between major versions of their Office products (unless you subscribe to Microsoft 365) and older versions of Office are not compatible with macOS Catalina or Big Sur.

If you have a version of Microsoft Office that is not compatible, you can either subscribe to Microsoft 365 (or if you already are, do a free upgrade to the current version of Office) 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 and very good Libre Office https://www.libreoffice.org/

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/

or Apple’s Pages and Numbers

I tried a one time purchase.. didn't work :(

Did you do it directly through Microsoft (i.e., not the Mac App Store)?

If so, can you give more details about "didn't work"?

Big Sur 11.2.3 not working well with my Microsoft office