na-adjective
unavailable; disabled; cannot be used
Used for functions, features, or items that are not available or have been disabled, often in software, services, or formal notices.
この機能は現在使用不可です。
This feature is currently unavailable.
アカウントが停止され、サービスが使用不可になった。
The account was suspended and the service became disabled.
Similar meaning, but 利用不可 often emphasizes that something cannot be utilized or accessed, while 使用不可 focuses on the inability to use or operate it.
Compound of 使用 (use) + 不可 (impossible, not allowed).