This is the 9127th most frequent Japanese word.
無効
Invalid; null; void.
Here, 無効 is used to describe the legal state of the contract, denoting 'invalid'.
この契約は無効となります。
This contract becomes invalid.
In this sentence, 無効 indicates the status of the login attempt caused by an error.
パスワードが間違っているため、ログインは無効です。
The login is invalid because the password is incorrect.
Here, 無効 refers to the acceptance status of the attempt, marking it as 'invalid' due to rules.