After upgrading from Telerik.Web.UI 2015.1.400.40 to 2017.2.621.45 the tooltip is not displayed any more.
The tooltip is on an click event from a button placed in a radgrid, the tooltip event fires and the code exceutes without any exception just as it did with the 2015 version, but the tooltip does not display on screen. The object to be displayed is a user control.