Dear Gianluca,
Thanks for your support and cooperation.
After downloading the demo, I opened the Start Lightstreamer excel RTD server sheet that's installed with demo but the same issue occurs but I think my machine connects sucessfully to your server as another demo 'DotNetStockListDemo.exe' is working correctly and recives updates from lightstreamer server normally I can provide yours with remote session to help me if you can ?

Thanks so much