@Josue Cunha ( Dy ) Looking at the error that you have shared, the issue is due to permissions issue. Please configure required permissions as documented here: https://learn.microsoft.com/en-us/azure/active-directory/authentication/tutorial-enable-sspr-writeback#configure-account-permissions-for-azure-ad-connect
Make sure you assign permissions to the account configured for On-prem AD Connector.
Also, check if the user who is trying to reset the password don't have "User cannot change password" and "Password never expire" checkbox selected in on-prem AD.
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