Problem solved by myself. Found out that Signal need to be activated every time you switch off the phone, problem is that in the Autorizations menu of the Settings when you open the Signal APP this function is not much visible and is little confusing, in my case for exmple I could see in light grey “active” but indeed it was not active I had to close it and activate again, after it was working. Also the message warning that Signal need to be activated remain on the screen less than one second and difficult to understand what you have to do. In any case thanks for your answer, Kasperky is the best ….. Ennio