excel on an old imac

Microsoft has retired all but the current Microsoft 365 subscription and either of Office 2019/2021 for Mac. In Fall 2022, after Apple released Ventura, Microsoft also dropped support for macOS Catalina and any MS Office software installed on Catalina can continue to be used (but not [re]installed) without any further updates from Microsoft.

If you want current Microsoft software update support, you will need to have a Mac that can upgrade to Big Sur (11.*) or later. In Fall 2023, Microsoft will again drop support for Big Sur, as they follow Apple's three-year support window.

kees1956 wrote:

Have problems updating Excel on my Mac

What version MacOS?

What version Microsoft Office?

Old Office versions are no longer supported and new versions of Office require newer operating systems.