First, you want to make sure that you can ping the device you are trying to simulate a Call on.
Then make sure it is not the Firewall/Security Software that is preventing the Call Simulator from working.
Also, make sure you are running the Call Simulator as an Administrator.
Kapersky Antivirus is Known to prevent the Call Simulator from transmitting packets.
De-activating Kapersky Antivirus may not fix the problem as it may need to be uninstalled to allow it to work.