A password policy defines the rules for password use in the Policy Manager, such as the length of a password, characters that must be included, when the password expires, how often passwords can be reset, etc.
Is it possible to disable Password Expiration for a specific account?
In Internal Identity Provider Password Policy, "Password Expiry" is checked OFF.
As per docops explanation, changes to the password policy do not apply to existing administrative users until they change their password.
Therefore, first change the password for the account. Then, if the "Password Expiry" is checked OFF, Password Expiration is disabled.