Custom Dashboard Widget

I have installed and activated the custom dashboard widget, and which shows on the dashboards of my test multisite platform, however the content of the widget does not show. Are you supposed to keep the following code in the content area:

<!--- custom content goes here --->

I deleted this code, and when I added the code back it still does not work. Deactivating and reactivating the plugin also does not help.

Can someone please assist.