activate my 365 account for office in Mac

This error is usually an Office licensing issue on Mac.

First, close all Office apps, then open Finder > Applications > Microsoft AutoUpdate and install all available Office updates. Microsoft has recently fixed the “0x0 / License not found” issue through updates:

https://support.microsoft.com/en-us/support/known-issues/unknown-error-0x0-license-not-found-error-microsoft365-macos

Then check https://account.microsoft.com/services and make sure your Microsoft 365 subscription appears under the same account you are using in Office.

If the subscription is active but Office still asks you to subscribe, use Microsoft’s License Removal Tool, then reopen Word or Excel and sign in again with the account that purchased Microsoft 365:

https://support.microsoft.com/en-us/microsoft-365-activation-licensing/how-to-remove-office-license-files-on-a-mac

This normally resolves the activation loop without reinstalling Office.