iPhone 5s wifi syncing with iTunes 11.4 just not working....

So - as I normally do - I press sync with iTunes - nope nothing happening.. so go to iTunes and no - my iPhone not showing (or my iPad) - plug usb in to sync - unplug usb (leaving wifi sync ticked) and iPhone does not show again .. tried shutting down, restarts etc - but nothing - I am not connected via wifi no matter what. Anyone suggest anything please? I have obviously misses a setting somewhere?