The Link Troubleshooting function of the Call Simulator Client relies upon ICMP responses on the Windows clients. The windows firewall in some cases will block the ICMP responses from reaching the system and cause the Link Troubleshooting feature to show incorrect information.
Here is how to create a Windows Firewall Rule to allow ICMP responses.
"Windows Firewall with Advance Security
Select Inbound Rules
On the Actions Bar Select "New Rule"
Select "All Programs"
Protocol Type: Select "ICMPv4"
Select The Profiles you want to use
Option: Give the Rule a name and Description