Gantt hiding all columns, then adding back in won't render.

As seen in the hiding columns example:

If you hide all columns, then want to add some back in, they won’t show up. Any thoughts on how this could be fixed? Right now I’m just calling gantt.render() after a user selects the columns they want to see, but it won’t work in this special case.

we’ve confirmed a bug, will try to provide you a fix in a nearest time.
As a workaround for now, try adding this code:

gantt.attachEvent("onBeforeGanttRender", function(){ if(!gantt.config.grid_width) gantt.config.grid_width = 200; });