R - Geoplots Not Showing in R Studio

I ran the sample code from the R documentation for a bubble map of the population of the US. I am running the code in RStudio. The code runs successfully but the map does not generate - only title and legend. Does anyone know how to correct?

All other sample code (box plots, scatter plots, etc) seems to work correctly.

Thank you.

See https://github.com/ropensci/plotly/issues/356 for more info about this issue.