Processes in Microsoft 365 for setting up Office apps, redeeming product keys, and activating licenses.
Hello Marcus Keyworth,
This might be caused by an outdated Office version, corrupted files transferred from the old Mac or saved sign-in information preventing activation.
First, update macOS under System Settings > General > Software Update. Then open an Office app and select Help > Check for Updates > Update All.
If the problem continues, completely uninstall Office, restart the iMac, then reinstall it from your Microsoft account under Services & subscriptions. After installation, open an Office app and allow Microsoft AutoUpdate to install all available updates.
You can also start the Mac in Safe Mode, open Office once, then restart normally. This also worked for some users after a macOS upgrade.
Disclaimer: While this is not a Microsoft website, it is the official site of Apple.
You can also create a temporary new macOS user account and test Office there. Go to System Settings > Users & Groups > Add User, sign in to the new profile, open Word, and try activating Office.
If the issue continues, please let me know your current macOS and Word versions, and whether the sign-in window displays an error or remains stuck loading.