For you and everyone else, most of the time the issue is caused by Sony's "Smart Connect" App. You'd think Sony's developers would test their updates! If you just disable the app completely, the headphone jack works without any issues! If after that your headphones still aren't picking up, you can chalk it to using headphones with remote (ie 3 rim headphone jack) and some not all work (my JBL's dont, but Sonys ones that came with the phone do as well as my Sennheisers) To disable the app completely (on Marshmallow Android) --> App Draw / Settings / Apps (make sure All Apps is selected) / Smart Connect Force Stop and then Disable. Rebooting the phone will still keep the App disabled so you dont need to do this continously. Also you dont need another 3rd party app like Soundabout. Hope this helps!
... View more