Hello @İlker Arslantürk , Thank you for reaching out to us.
Could you please check and confirm the following points:
1.Please check Azure AD audit logs and sign in logs and see if you seeing any success events for password reset and check if there is any error which help in isolating the cause, if you see any reason or error, kindly share it with me.
2.I request you to have look into the general limitation article:https://learn.microsoft.com/en-us/azure/active-directory/authentication/howto-sspr-windows#general-limitations
3. Let me know if the user is Cloud user or Synced user, as i suspect that after resetting the password, user is able to login to cloud services only, Is password writeback is enabled in the environment?
4. Please have a look into the troubleshooting guide for SSPR as well:https://learn.microsoft.com/en-us/azure/active-directory/authentication/troubleshoot-sspr
Let me know if you have any questions related to the above steps and if above information helped you please upvote the thread, it will help other community members which come across the similar issue.