FullCalendar header buttons missing

I am using fullCalendar as below and have defined header section, everything works ok except header where it's only showing title but next, prev, month view etc buttons are missing

if I remove word 'title' it removes title so it seems to be doing something but just not showing buttons, any ideas why? am I missing something? my code looks like below:

jQuery('#calendar').fullCalendar({
    header: {
        left: 'prev,next today',
        center: 'title',
        right: 'month,agendaWeek,agendaDay'
    },
    eventSources:
    [{
        url: url,
        color: '#ffdce5',
        textColor: 'black' 
    }]

})

Having just had the same problem I suspect your issue is that you're missing the media="print" attribute on the fullcalendar.print.css style sheet link.