Pagination from server side not working

Hi,
All my datatables are working correctly, but one of them simply doesn't show pagination (whatever the number it always shows 1 page)
The server side result is like this
{"iDisplayLength":0,"iDisplayStart":0,"iColumns":0,"iSortingCols":0,"iSortColumnIndex":0,"iTotalRecords":43,"iTotalDisplayRecords":10,"aaData":[[...my data...]]}

What could be wrong ?

Thank you.