Sidebar tabs not recognising tabname argument

Question

I am trying to create a shiny dashboard with three tabs. The first tab is supposed to include a leaflet map, I have then tried to add a second tab to include a page for a dataframe. However, the dataframe and its title is being added to the bottom of the leaflet map page, despite specifying a different tab name.

I am new to shiny so any help is appreciated.

code specific to the question is as follows:

library(shiny)
library(leaflet)
library(RColorBrewer)
library(shinythemes)
library(dplyr)
library(shinydashboard)
library(rgdal)
library(htmltools)
library(ggplot2)
library(DT)

#### UI #############################################################

### header ###
header <- dashboardHeader(
  title = "World Happiness Dashboard",
  titleWidth = 400
)


### Body content ###
body <- dashboardBody(
  tabItems(
    # First tab content
    tabItem(tabName = "Map",
            fluidRow(
              column(
                width = 12,
                     box(
                       title= "Global Levels of Happiness, GDP, Population Density and Covid Stringency", 
                       solidHeader = TRUE,
                         width = NULL, height = 530,
                         leafletOutput("map",height=470),
                         status='primary')
              )
            )
    )
  ),
    
    # Second tab content
  tabItem(tabName = 'data',
          fluidPage(
            h1('Data Table'),
            dataTableOutput("maptable")
          ))
  )


sidebar <- dashboardSidebar(
  width = 180,
  sidebarMenu(
    menuItem("Map", tabName = "Map", icon = icon("globe"), badgeLabel = "Start Here!", badgeColor = "green"),
    menuItem("Data", icon = icon("list", lib = "glyphicon"), tabName = "data")
  )
)


### ui ###
ui <- dashboardPage(
  title = "Happiness Data Visualisation",
  skin = 'blue',
  header,
  sidebar,
  body
)

#### Server ###################
server <- function(input, output, session) {
  
  
  #### output ####
  ## output: leaflet map
  output$map <- renderLeaflet({
    
    map <- worldCountries %>%
      leaflet() %>%
      addTiles() %>%
      setView( lat=10, lng=0 , zoom=2) %>% #sets default map pan
      addPolygons(### happiness #########
                  data = worldCountries,
                  fillColor = ~mypalettewhi(happiness_score), 
                  stroke=TRUE, 
                  fillOpacity = 0.9, 
                  color="white", 
                  weight=0.7,
                  label = mytext,
                  labelOptions = label,
                  highlightOptions = highlight,
                  group = "World Happiness Index"
      ) %>%
      addPolygons(### GDP #################
                  data = worldCountries,
                  fillColor = ~mypalettegdp(gdp), 
                  stroke=TRUE, 
                  fillOpacity = 0.9, 
                  color="black", #black is added as highlight as yellows will blend
                  weight=0.7,
                  label = mytext,
                  labelOptions = label,
                  highlightOptions = highlightgdp,
                  group = "GDP"
      ) %>%
      addPolygons(### population #################
                  data = worldCountries,
                  fillColor = ~mypalettepop(pop_density_log), #log is used to diminish extreme values
                  stroke=TRUE, 
                  fillOpacity = 0.9, 
                  color="white", 
                  weight=0.7,
                  label = mytext,
                  labelOptions = label,
                  highlightOptions = highlight,
                  group = 'Population Density'
      ) %>% 
      addPolygons( ### covid stingency ##############
                   data = worldCountries,
                   fillColor = ~mypalettecovid(avg_covid_score), 
                   stroke=TRUE, 
                   fillOpacity = 0.9, 
                   color="white", 
                   weight=0.7,
                   label = mytext,
                   labelOptions = label,
                   highlightOptions = highlight,
                   group = "Covid Stringency Score"
      ) %>%
      addLayersControl( #controls layers
        baseGroups = c("World Happiness Index", "GDP", "Population Density", "Covid Stringency Score"), #base groups indicates these will be toggled between groups
        options = layersControlOptions(collapsed = FALSE) 
      ) %>%
      addLegend( #happiness legend
        values=~happiness_score, 
        opacity=0.9, 
        title = "World Happiness<br /> Index Score", 
        position = "bottomleft",
        colors = c('#ffffb2', '#fed976', '#feb24c', '#fd8d3c', '#fc4e2a', '#e31a1c', '#b10026'),
        labels = c("Less Happy", "", "", "", "", "", "More Happy"),
        group = "World Happiness Index" #group it belongs to
      ) %>%
      hideGroup(c('World Happiness Index','GDP', 'Population Density', 'Covid Stringency Score')) %>%
      showGroup('World Happiness Index')
  })
  
  #### update legend when the selected layer group changes ######################
  
  observeEvent(input$map_groups, {
    my_map <- leafletProxy("map") %>% clearControls()
    
    if (input$map_groups == 'World Happiness Index'){#### Happiness Legend ####
      my_map <- my_map %>%
        addLegend(
          opacity=0.9, 
          title = "World Happiness<br /> Index Score", 
          position = "bottomleft",
          colors = c('#ffffb2', '#fed976', '#feb24c', '#fd8d3c', '#fc4e2a', '#e31a1c', '#b10026'),
          labels = c("Less Happy", "", "", "", "", "", "More Happy"),
          values = worldCountries$happiness_score
        )
    }else if (input$map_groups == 'GDP'){ #### GDP Legend ####
      my_map <- my_map %>%
        addLegend( 
          opacity=0.9, 
          title = "GDP (US$)", 
          position = "bottomleft",
          colors = c('#ffffd3', '#d9f0a3', '#addd8e', '#7bce7c', '#41ab5d', '#238443', '#005a32'),
          labels = c("Lower GDP", "", "", "", "", "", "Greater GDP"),
          values = worldCountries$gdp
        )
    }else if (input$map_groups == 'Population Density'){
      my_map <- my_map %>%
        addLegend( #### pop density legend ####
                   opacity=0.9, 
                   title = "Population Density<br />  (per km\u00B2)", 
                   position = "bottomleft",
                   colors = c('#f2f0f7', '#dadaeb', '#bcbddc', '#9e9ac8', '#807dba', '#6a51a3', '#4a1486'),
                   labels = c("Less Dense", "", "", "", "", "", "More Dense"),
                   values = worldCountries$pop_density_log
        )
    }else{
      my_map <- my_map %>%
        addLegend( #code for covid legend
          opacity=0.9, 
          title = "Covid Stringency Score", 
          position = "bottomleft",
          colors = c('#eff3ff', '#c6dbef', '#9ecae1', '#6baed6', '#4292c6', '#2171b5', '#084594'),
          labels = c("Less Stringent ", "", "", "", "", "", "More Stringent"),
          values = worldCountries$avg_covid_score
        )
    }
  })

  ###### add data table ##################
  output$maptable <- renderDataTable(cleantable)  
  }



#### Run App ####
shinyApp(ui = ui, server = server)