iPhone to iMac

Why will my iPhone no longer connect to my iMac or to any other Mac. I need to use file sharing to get a sound file from the phone to the computer. I have restarted everything, all of the OS stuff is up to date. When I go into iTunes the iPhone is not connected and not available. This is the kind of thing which infuriates me, if they are going to stop supporting something they need to warn you first. There is no alternative will have to throw a two hour sound file in the bin!