Do you have a reproducible example of on_click not working?
Does the original post work for you Mr. @Marc ?
on_click callbacks should have an event in args
def _download_callback(self, event):
pn.state.notifications.success('_download_callback')
def __init__(self):
self.download_button = pn.widgets.Button(name="Download")
self.download_button.on_click(self._download_callback)
super().__init__()
The error is nested in the browser console
