This error means that your local Word instance cannot reach the Microsoft app catalog to get the add-in details. Basically, your local machine cannot "talk" to the app catalog for some reason. This may be for a variety of reasons:
- No internet connection
- Blocked by firewall
- Access disabled by a security policy
- Add-in installation disabled by an administrator for Office applications
Please reach out to your IT team or system administrator for further assistance, to make sure you have the rights to install add-ins for Office and there are no network or security policies blocking you.