Can not display a popover on a custom button on task row

Gantt
#1

Can not display a popover on a custom button on task row

#2

Hello Kevin,
Unfortunately, I cannot reproduce it:
http://snippet.dhtmlx.com/8e81661ba
If you want to show a separate tooltip for the button, you need to add the following command:

gantt.ext.tooltips.tooltipFor({
  selector: ".css_class_name",
  html: function(event, domElement){
    return "Your text"
  }
});

Here is an example:
http://snippet.dhtmlx.com/4119a5ed6

If that doesn’t help you, please give me more details about your case and reproduce the issue in the snippet.