I can't save edited excel files. Why?

I have macOS Tahoe, version 26.5.2. Subscription is current and renews each year. Will renew again in August.

First, see if you can update your Office apps. Open Word for example, click on the 'Help' tab >Check for Updates. Make sure you choose Update All when prompted. Let the process run through, can take a bit time. See if that works.

Otherwise, use the Update method in this article: https://support.microsoft.com/support/known-issues/unknown-error-0x0-license-not-found-error-microsoft365-macos

If it still doesn't work, please uninstall the apps. Follow the instructions here for complete uninstall.

https://support.microsoft.com/office/office-for-mac/troubleshoot-office-for-mac-issues-by-completely-uninstalling-before-you-reinstall

Then reinstall this way:

If you signed up via Apple App Store, then download and install from the App Store.

If you signed up via Microsoft directly, please go to https://www.office.com

Sign into the Microsoft account you used for the subscription. Click on the 9-dot icon on the upper left > More apps.

Then on the upper right, click on "Install apps". This will now download the installer file. Once downloaded, click on the file to install. It will install the Desktop version of the apps for you then.

https://support.microsoft.com/office/download-install-or-reinstall-microsoft-365-or-office-2024-on-a-pc-or-mac-4414eaaf-0478-48be-9c42-23adc4716658

If it still doesn't work, download the updater https://support.microsoft.com/office/office-for-mac/troubleshoot-microsoft-autoupdate-in-microsoft-365-and-office-for-mac