C# Tooltip not appearing on "Show"

To fullfill a requirement I have to show a tooltip manually for 30 seconds. According to msdn I just have to use the "Show" method.

toolTip.Show(QuestionHelpText, btnHelp, 30000);

But I only get the standard tooltip behavior, meaning that the message appears half a second after my click (only because the mouse pointer is still over the button). I tried some variations like

toolTip.Show(QuestionHelpText, btnHelp);

but still, nothing happens.

Does anybody have an idea why that is?

Thanks