You have issues to reset a user password when an account was already a migrated portal user.
Symantec Email Security.Cloud
Portal user is using a new log in method via SSO, therefore any password reset queries must be performed by the account owner him self.
The account owner or portal user must either use the self service via okta to reset their password or try to use the Log in with Symantec option. If Broadcom's SSO is being used, for that you go to this link and click as illustrated below: https://login.broadcom.com/
If the issue persists, you can contact the Technical Support.