If the call to 2N® Helios IP was estabilished (you can verify it e.g. based on the trace) but there is no voice and video on your IP video phone or softphone, then the problem can be in the configuration of 2N® Helios IP - there is enabled "Automatic pick up" but the activation mode is set to "Manual". It means that activation code is required. For proper function you have to change "Activation mode" to "Automatic" as you can see in the picture below.
Note: there are two pictures - the first one is for FW version 2.5.0 and older and the second one is for FW version 2.6.0 and newer (new web interface)!