Hello @Paulo Ramos,
Thank you for posting your query on Microsoft Q&A.
I see that you have two admin users with the Helpdesk Administrator and Password Administrator roles assigned, but they are unable to reset user passwords from the Azure Portal.
Based on our community answers, I see you have verified all the prerequisite of this issue. However, there is another limitation you should check.
User Account Admins cannot update normal user's passwords, if the user belongs to a AAD group where Assignable to role is True.
Please verify if the user is a member of any Azure AD group with "Microsoft Entra roles can be assigned to the group" set to True. You can determine this by going to the list of groups in the All Groups blade, enabling the "Role assignments allowed" column.
If the user is part of such a group, try removing them from the group and assigning the role directly to the user instead. Check if this resolves the issue.
If the problem persists, please send an email to azcommunity@microsoft.com referencing this issue with the subject line "ATTN: pothurajur" and include a link to the current thread.
I hope this information is helpful. Please feel free to reach out if you have any further questions.
If this answers your query, do click Accept Answer and Yes for was this answer helpful. And, if you have any further query do let us know.
Thanks,
Raja Pothuraju.