When launch SR5500 TestKit GUI, after a while, an error will be given like below:
This error is due to the missing of service pack 1 installation for dotnet v1.1, simply go to microsoft webpage to get this download here
https://www.microsoft.com/en-us/download/details.aspx?id=33
After finish the installation, restart PC to let this installation take effect, relaunch TestKit again, and it should fix the error.