vCenter SSO 5.1 Administrator Password has expired. Password reset is failing. Please help.

Hello Gurus,

We have a vCenter 5.1 Server, whose SSO administrator@vsphere.local password has expired recently. We tried to do a password reset as mentioned in the below link, but it is failing as shown in the attachment. We do not have any other user accounts that has rights on the SSO. Also, since there is some issue with identity source, no one is able to login for now.

As you know, VMware support has ended since it is 5.1. Please help.

VMware vSphere 5.1

Thanks.