Processes in Microsoft 365 for setting up Office apps, redeeming product keys, and activating licenses.
This work around temporarily fixes the problem, but IT DOES NOT SOLVE IT. The problem will always return.
Uninstall all remnants of Office installations by using the Uninstall support tool (see Option 2 in the article at https://support.microsoft.com/en-us/office/uninstall-office-from-a-pc-9dd49b83-264a-477a-8fcc-2fdf5dbf61d8).
Run the System File Checker to verify the Windows system files (https://support.microsoft.com/en-us/windows/using-system-file-checker-in-windows-10-365e0031-36b1-6031-f804-8fd86e0ef4ca). Also install any pending Windows updates.
Once those steps are complete, reinstall Office using your account at https://account.microsoft.com/services. Note that organization/business versions are managed via https://portal.office.com. If you run into activation issues, also see https://www.poremsky.com/office/remove-office-licenses-windows/.
If the problem remains, continue troubleshooting add-ins; see https://docs.microsoft.com/en-us/office/troubleshoot/word/issues-when-start-or-use-word.