I am recently trying to make a basic interactive Shiny app, where users can also download the pdf files as well. And, I am receiving Warning: Error in render: could not find function "render" error when trying to run the app. I could not figure out what the problem is. Here is my code so far

library(shiny)
library(rnaturalearth)
library(DT)
library(leaflet)
library(readxl)
library(tidyverse)
library(scales)
library(ggtext)
library(showtext)
library(showtextdb)
library(plotly)
library(shinyjs)

# Create a fake dataset with population and economy information
fake_data <- read_excel("data.xlsx")


ui <- fluidPage(
  ## enables shinyjs
  useShinyjs(),
  sidebarLayout(
    sidebarPanel = sidebarPanel(
      ## Select Players
      selectizeInput(inputId = "selected_city", label = "Şehir Seçiniz", choices = unique(fake_data$Vilayet), multiple = FALSE,
                     width = "100%"),
      hr(),
      ## Start these buttons off as disabled
      disabled(actionButton("render_report_button","Render Report",width = "100%")),
      disabled(downloadButton("download_rendered_report", "Download Report", style = "width:100%;"))
    ),
    mainPanel = mainPanel(
      ## simple plots
      DTOutput(outputId = "fake_table")
    )
  )
)

### Server

server <- function(input, output, session){
  
  
  selected_city_data <- reactive({
    
    req(input$selected_city)
    
    fake_data %>% 
      filter(Vilayet %in% input$selected_city)
  })
  
  ## Make the table
  fake_table_raw <- reactive({
    selected_city_data() %>% 
      datatable(options = list(paging = FALSE, searching = FALSE, info = FALSE))
  })
  
  ## Send plots to output
  output$fake_table <- renderDT({fake_table_raw()})
  
  
  ## enable rendering if players are selected, else, disable everything
  observeEvent(input$selected_city,{
    if(!is.null(input$selected_city)){
      enable("render_report_button")
    }else{
      disable("render_report_button")
      disable("download_rendered_report")
      report_loc(NULL)
    }
  }, ignoreNULL = FALSE)
  
  
  ## Render report on click. store result to reactive val
  report_loc <- reactiveVal()
  observeEvent(input$render_report_button,{
    
    ## always write to a new dir
    output_dir <- tempfile()
    dir.create(output_dir)
    
    ## store data from shiny in env for report, getting values from reactive
    render_env <- new.env()
    render_env$selected_city_data <- selected_city_data()
    
    render(
      input = "report.Rmd", ## capitalization must match
      output_dir = output_dir,
      envir = render_env
    )
    
    ## update report_loc to have rendered file
    report_loc(list.files(output_dir, full.names = TRUE))
  })
  
  ## enable downloading if report is rendered
  observeEvent(report_loc(),{
    if(!is.null(report_loc())){
      enable("download_rendered_report")
    }else{
      disable("download_rendered_report")
    }
  }, ignoreNULL = FALSE)
  
  ## download rendered report!
  output$download_rendered_report <- downloadHandler(
    filename = function(){
      basename(report_loc())
    },
    content = function(file){
      file.copy(report_loc(), file, overwrite = TRUE)
    }
  )
  
}

shinyApp(ui = ui, server = server)

I appreciate any suggestions, comments and/or feedback on how to figure out this problem. Thank you for your attention beforehand.