I have tried sending the password reset link to this admin repeatedly but it doesn't seem to be working. Or I have an admin that doesn't have a valid email address. Can I set their password by hand instead of sending the password reset link email?
No for security purposes it is not possible for a Luminate administrator to assign a password to another administrator instead of sending the password reset link. Try changing the admin's email address to some other email address if the admin is not receiving the email.