Smart Rendering not working

Hello everyone, i have a gantt that load hundred of data from REST API, I took to around 10-30 second to render the data to my gantt. I all the recommendation from this page but it still slow, the smart rendering is not working in my gantt, can anyone tell me what I did wrong in my code.

Here is my code snippet :

gantt.config.show_progress = false; gantt.config.show_task_cells = true; gantt.config.smart_rendering = true; gantt.config.smart_scales = true; gantt.init("project_scheduler_gantt", new Date("{{ selected_project.project_start_date }}"), new Date("{{ selected_project.project_end_date }}")); gantt.load("/api/scheduler/{{ }}/?format=json", "json");

and yes, I’ve already added the <script type="text/javascript" src="/static/third_party/dhtmlx/dhtmlxGantt_v4.2.1/codebase/ext/dhtmlxgantt_smart_rendering.js"></script> in my html page


Do you get any errors in console?
Do you use PRO version of DHTMLX Gantt?