404可能是一个错误的urlManager规则或一个缺失，你从这里开始。

为yii配置CORS，请确保允许OPTIONS操作/动词。
另请参阅此处的文档：CORS config
即：

public function behaviors()
{
    $behaviors = parent::behaviors();

    $behaviors['corsFilter'] = [
        'class' => \yii\filters\Cors::className(),
        'cors' => [
            'Origin' => ['*'],
            'Access-Control-Request-Method' => ['GET', 'POST', 'PUT', 'PATCH', 'DELETE', 'HEAD', 'OPTIONS'],
            'Access-Control-Request-Headers' => ['*'],
            'Access-Control-Allow-Methods' => ['GET', 'POST', 'PUT', 'PATCH', 'DELETE', 'HEAD', 'OPTIONS'],
            'Allow' => ['GET', 'POST', 'PUT', 'PATCH', 'DELETE', 'HEAD', 'OPTIONS'],
            'Access-Control-Allow-Credentials' => null,
            'Access-Control-Max-Age' => 86400,
            'Access-Control-Expose-Headers' => []
        ]

    ];
    return $behaviors;
}