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After you configure the Azure AD self-service password reset all the users must complete the SSPR registration at https://aka.ms/ssprsetup
another consideration is that for your users to be able to comply with your AD's password policies on Premises, you should change the hybrid authentication method from Password Hash Synch to Pass-through Authentication
The extra mile is you Enable Azure Active Directory self-service password reset at the Windows sign-in screen
Hope this helps!
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