Office Home & Business 2019 license no longer recognized after reinstall ("No license found")

This issue isn't related to hardware,it's a known issue affecting all Office 2019 Mac users.

Microsoft used an embedded license validation certificate for Office 2019 Mac. This certificate expired on July 13, 2026. Main support for Office 2019 Mac ended in October 2023, and extended support in October 2025. Therefore, Microsoft hasn't issued a new certificate. Once the certificate expired, the license validation system stopped working.

Office only opens in view/print mode; creation, editing, and saving functions are disabled. Reinstalling, clearing the cache, or trying different versions doesn't work because the problem is with the certificate, not the device. This isn't related to older Mac hardware; it occurs on newer devices as well.

Solution options:
Free: Use the web versions of Word/Excel/PowerPoint via Office.com.
One-time purchase: Office 2024 for Mac. 
Subscription: Microsoft 365.