Processes in Microsoft 365 for setting up Office apps, redeeming product keys, and activating licenses.
Hello Neale,
I would check whether or not your account allows basic authentication (Microsoft 365). Just recently, M365 began enforcing MFA, which you would need to allow an app password. App passwords must be allowed in your tenant as well.
Enforce Azure AD Multi-Factor Authentication with legacy applications using app passwords
https://learn.microsoft.com/en-us/azure/active-directory/authentication/howto-mfa-app-passwords
If this is helpful please accept answer.