Cannot shut off AIS silent mode to off

Good Morning , I have tried to search FAQ for the answer to a dead end
My AIS silent mode stays on all the time and I cant switch it to off. This has been since I bought he E127. I read the AIS silent mode entry on this forum but cant understand it. .........Any ideas . I am using lighthouse 11 and I am hoping installing 17 will help .
THANKS FOR ANY HELP
ALTERBOY