@Patrick Williams Thank you for reaching out to us, As I understand you are trying to reset the password of an Global admin account (which is a Microsoft account example live.com or hotmail.com), when you click on the reset password option on the portal, its not letting you to change it.
This is by design, even as a Global admin account we cannot reset the password of a guest account (who is a global admin in your directory), same has been documented here - https://learn.microsoft.com/en-us/azure/active-directory/fundamentals/users-reset-password-azure-portal
Let me know if you have any further questions, feel free to post back.
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