按官网教程https://www.3cx.com/docs/cfd-creating-outbound-dialer/配置VFD，导入3cx call flow apps后，出现错误，如下：
:[33855..33878)E: (751,36)-(751,59): Error CS1061: ‘Callflow.ExtensionStateHelper’ does not contain a definition for ‘isThereAnyFreeExtension’ and no accessible extension method ‘isThereAnyFreeExtension’ accepting a first argument of type ‘Callflow.ExtensionStateHelper’ could be found (are you missing a using directive or an assembly reference?)
return instance.isThereAnyFreeExtension();
^^^^^^^^^^^^^^^^^^^^^^^
请问是哪里错了?
