It would helps if you actually explained what method you were trying or added the project with the widget.
But lets assume you are using the HTML Widget with •specified URL
The common problem is not hit the enter button after typing out the URL or move focus to another part of the UI.
This is a slight design fault in that the url entered is not registered until the textfield loses focus.
If you leave it in focus as shown here with the blue highlight around the textfield then it will not work
You need to press the enter key or making sure focus has gone elsewhere.
Which will look like this.