Interactive R custom visuals not displaying in Power BI Desktop

I tried several online tutorials on how to begin creating interactive R custom visuals (such as the link shown below), and followed all these tutorials carefully. 

   http://radacad.com/interactive-map-using-r-and-power-bi-create-custom-visual-part-1

Every thing seemed to go as expected and according to the instructions, all the way to (apparently successfully) importing the packaged .pbiviz file as a custom visual into the set of available charts visible in the visualization pane of Power BI Desktop.

However, when I click on the newly available custom visual icon, only a generic empty chart tile is placed on the report page. 

The same unssuccessful end result happens no matter which sample interactive R custom visual I tried, including the one from the sampleRHTMLVisual template, which I copied and pasted below the script.r file:

source('./r_files/flatten_HTML.r')

############### Library Declarations ###############

libraryRequireInstall("ggplot2");

libraryRequireInstall("plotly")
####################################################

################### Actual code ####################

g = qplot(`Petal.Length`, data = iris, fill = `Species`, main = Sys.time());

####################################################

############# Create and save widget ###############

p = ggplotly(g);

internalSaveWidget(p, 'out.html');

####################################################

I am fairly good with R; and have successfully implemented many R scripts to run within Power BI Desktop, and have also published them onto the Power BI Pro online service displaying static R visuals.   However, I am a relative beginner with Power BI, and have not (yet) created any custom visuals.  I'm excited about the ability to create interactive R custom visuals in Power BI. 

• I installed the latest LTS version (8.12.0) of Node.js on my 64-bit Windows 10 Pro computer.
• Running 64-bit R 3.5.1 on this Windows 10 machine.
• All required R packages are installed.

Would appreciate assistance to overcome this hurdle.