why can't I download excel

The current version of Excel requires macOS 11.0 or later.

I understand you want to download Microsoft Excel from the Mac App Store. Is that correct? Are you using this link?

https://apps.apple.com/us/app/microsoft-excel/id462058435?mt=12

If so please explain the reason you are unable to download it. Describe what happens when you try. Perhaps this will help: If you can't connect to the App Store, iTunes Store, or other Apple services - Apple Support.

As dialabrain noted though, the current version will not run in Catalina. You need to upgrade macOS to Big Sur or Ventura first: How to download macOS - Apple Support describes possible upgrade options.

cclark2018 Said:

"why can't I download excel: I have a iMac and can't download excel any clues"

-------

Contact Microsoft Support:

They are the developers of the software. Ask them about overcoming unsuccessful installations and about upgrading. Start Here:  Microsoft Contact Us Virtual Agent - Microsoft Support