Processes in Microsoft 365 for setting up Office apps, redeeming product keys, and activating licenses.
What exact macOS version are you running?
Did you purchase/set up Microsoft 365 directly through microsoft or through the Apple App Store?
If your macOS is below version 12 (Monterey), updating Office won't fix this, since Microsoft requires macOS 12+ as of a licensing change from July 13, 2026, and no version can work around that on an older Mac.