Any user that has ISA permission on a Managed System or Account should be able to access the "Current Password" tab on the Account. This will allow you to retrieve the password that TPAM believes to be the current password.
If the Current Password is greyed out, that means you do not have ISA permission on that System/Account. You will need to grant yourself temporary permission on that System/Account. If you are not an Administrator, you will need to get another user with ISA permission to retrieve the current password for you.
If you successfully retrieve the current password, but it does not work on the remote system, the password may not be valid. This could be due to a loss of connection between the TPAM appliance and the remote system which caused the password to be improperly changed, or the password for that account may have been changed manually on the remote system itself.