Hi and welcome! You haven't added a basemap or any markers to your leaflet map, so I wouldn't expect anything to be displayed. I would recommend starting with the examples on the Leaflet for R site. They have code for many different types of leaflet maps.
For instance, are you able to make this first introductory leaflet map?
library(leaflet)
leaflet() %>%
addTiles() %>%
addMarkers(lng=174.768, lat=-36.852, popup="The birthplace of R")