There are two possible reasons for this error:
- The password that you have provided in the body of your token acquisition call is a temporary password. Temp password is marked as expired and postman doesn't provide an option for you to reset that. If it is a temp password, please try to sign-in to portal.azure.com or portal.office.com and set a permanent password for the user account you are using.
- The user account you are using is a federated account and is not synced to the Azure AD. In that case, please follow the instruction provided in blog post here: https://medium.com/@amanmcse/ropc-username-password-flow-fails-with-aadsts50126-invalid-username-or-password-for-federated-90c666b4808d
Hope this helps.
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