ITunes abruptly stopped recognition of phone

Imac Itunes wont see plugged iphone se with music app eevn though it's never been a problem. what changed at 8pm last night, lol. They both play independent on the computer and phone but it just stopped recognition so I cant sync and modify it, etc... Please, and thankyou for any advice. I phot starts when plugged in and connect but itubes and finder dont see it past an icon.