I cannot use ICOMDeviceSettingsExt, I get null object in SDK 3.7.

Hi, I am developing an application using Plantronics SDK v3.7.51277.30194. After creating a session, when attaching the device I am obtaining all objects derived from m_device.HostCommand.                     m_hostCommand = m_device.HostCommand as ICOMHostCommand;                     m_hostCommandExt = m_device.HostCommand as ICOMHostCommandExt;                     m_deviceSettings = m_device.HostCommand as ICOMDeviceSettings;                     m_deviceSettingsExt = m_device.HostCommand as ICOMDeviceSettingsExt;                     m_advanceSettings = m_device.HostCommand as ICOMAdvanceSettings;                     m_atdCommand = m_device.HostCommand as ICOMATDCommand; The thing is that all objects are assigned correctly but m_deviceSettingsExt which is null.  I need to use the FindHeadsetLEDAlert property to activate/deactivate the LED, which contained in ICOMDeviceSettingsExt in my app. Am I doing anything wrong? Is this Interface different from the others? Thanks!