Emergency control systems do not support ECDs by default. A license must be purchased for the ECD feature in order to use them on emergency control systems. Please read How do I purchase control system upgrades to enable this feature.
The license status for a control system can be viewed from the ECD view in the add-ons section in grid view. If there is a green tick under the license column then that means it has been purchased. If there is a red circle with a line through it then it means the control system does not support the ECD license. If there is a blue square then it means the control system already supports it and does not need a license such as on application control systems etc. If there is an orange credit card icon then it means the license is able to be purchased.
Once you have the license and there is a green dot in the first column of the row in grid view then that means it is working and you can use ECDs like normal with your emergency control system.