Leaflet not working in R Shiny Package fullPage

Question

I am having trouble getting a leaflet map to display in R Shiny when using the fullPage package/theme. Anyone have any idea what could be going on here? Code works in all the othe Shiny themes I use, so I'm guessing it's something specific to fullPage? I only started playing around with this theme yesterday so certainly possible I'm missing something.

Full Example Below:

#
# This is a Shiny web application. You can run the application by clicking
# the 'Run App' button above.
#
# Find out more about building applications with Shiny here:
#
#    http://shiny.rstudio.com/
#

library(shiny)
library(fullPage)
library(leaflet)
library(highcharter)
library(glue)
library(tidyverse)

img1 <- "https://live.staticflickr.com/8081/8312400018_f53f23dac9_b.jpg"
# Define UI for application that draws a histogram
options <- list(
    sectionsColor = c('#F5F5F5'),
    parallax = TRUE
)

ui <- fullPage(
    menu = c("Home" = "home",
            "About" = "about",
             "Analytics" = "analytics",
             "Buy" = "section3",
             "Sell" = "section4",
             "Rent" = "section5",
             "Contact" = "contact"),
    opts = options,
    fullSectionImage(
        img = img1,
        menu = "home"
    ),
    fullSection(
        center = FALSE,
        menu = "about",
        br(),
        br(),
        fullContainer(
        tags$h1("Example")
        ),
        fullContainer(
        fullRow(
            fullColumn(
          p('Some text.'),
          br(),
          p('More text.')  
            )
        )
        ),
        fullRow(
            pre(
                
                code(
                    
                    img(src = 'https://pics.harstatic.com/office/395001.png', width = '50%', height = 'auto')
                    )
            )
        )
    ),
    fullSection(
        menu = "analytics",
        fullRow(
            fullColumn(
                h3("Column 1"),
                selectInput(
                    "dd",
                    "data points",
                    choices = c(10, 20, 30)
                )
            ),
            fullColumn(
                plotOutput("hist")
            ),
            fullColumn(
                plotOutput("plot")
            )
        )
    ),
    fullSection(
        menu = "section3",
        fullSlide(
            fullContainer(
                center = TRUE,
                h3("With container"),
                plotOutput("slideplot2"),
                shiny::verbatimTextOutput("containerCode")
            )
        ),
        fullSlide(
            center = TRUE,
            h3("Without container"),
            plotOutput("slideplot1")
        )
    ),
    fullSectionPlot(
        menu = "section4",
        center = TRUE,
        "fp",
        h3("Background plots"),
        fullContainer(
            sliderInput(
                "fpInput",
                label = "Input",
                min = 10,
                max = 100,
                value = 74
            )
        )
    ),
    fullSection(
        menu = "section5",
        fullSlidePlot(
            "slideSectionPlot1",
            center = TRUE,
            h1("Slide background plot")
        ),
        fullSlidePlot(
            "slideSectionPlot2"
        )
    ),
    fullSection(

        menu = "contact",
        fullContainer(
                    leaflet::leafletOutput('map')
        
            
        )
    )
)

server <- function(input, output, session){
    
    output$map <- leaflet::renderLeaflet({
        
        leaflet() %>%
            addTiles(group = "OSM (default)")
            
        }
    )
    
}

shinyApp(ui, server)