Error when publishing shiny app (full details inside)

Hi all,

This is the error when published:
An error has occurred
The application failed to start (exited with code 1).

Error in value[3L]: could not find function "leafletOutput"
Calls: local ... tryCatch -> tryCatchList -> tryCatchOne ->
Execution halted.

Edit 1!
After publishing, I also have this message in rStudio:
Warning in renderWidget(instance) :
Ignoring appended content; appendContent can't be used in a Shiny render call

Edit 2:
I have also tried adding leaflet::leafletOutput

Any help is much appreciated.

Cheers,
Michael

ui<-fluidPage(
  tabsetPanel(
    tabPanel(title = "Phone Calls",
             titlePanel("San Francisco Suspicious Occurences 311 Phone Calls"),
             leafletOutput("map")),
    tabPanel(title = "College Graduates by San Francisco Tracts",
             titlePanel("College Gradutes in SF"),
             leafletOutput("map2")),
    tabPanel(title = "Data Table",
             sidebarLayout(
               sidebarPanel(
                 selectInput("Description", "Select a type of call",
                             choices = police_data_july_2015$Descript)),
               
               mainPanel(
                 tableOutput("police_data_july_2015")
               )
             ) 
    )
  )
) 

server <- function(input, output) {
  output$map<-renderLeaflet({
    leaflet(data = police_data_july_2015) %>%
      addTiles() %>%
      addCircleMarkers(~X, ~Y,
                       popup = ~str_c("Suspicious Occurence" = Category),
                       label = ~Descript,
                       clusterOptions = markerClusterOptions()) 
  })
  
  output$map2 <- renderLeaflet({
    tmap_leaflet(map_ce_final)
  })
  
    output$police_data_july_2015 <- renderTable({
    descriptFilter <- subset(police_data_july_2015, 
                             police_data_july_2015$Descript == input$Description)
  })
}


shinyApp(ui= ui, server = server)