How to visualize multiple graph in shiny dashboard?

I tried to visualize all the graphs but the upper one did not appear. I want to know what is missing. the server code for the bar graph works but for the histogram dose not appear.

ui <- fluidPage(
  br(),
  titlePanel("Country Salary"),
  p("Explore the difference between people who earn less than 50K and more than 50K. You can filter the data by country, then explore various demogrphic information."),
  
  # TASK 2: Add first fluidRow to select input for country
  fluidRow(
    column(12,
           wellPanel(selectInput("country", "Select Country",c("United-States", "Canada", "Mexico", "Germany", "Philippines"))  # add select input
           )
    )),
  
  # TASK 3: Add second fluidRow to control how to plot the continuous variables
  fluidRow(
    column(3,
           wellPanel(
             p("Select a continuous variable and graph type (histogram or boxplot) to view on the right."),
             radioButtons( "continuous_variable","Continuos variable",choices = c("age" , "hours_per_week")),   # add radio buttons for continuous variables
             radioButtons("graph_type","Graph", choices = c("histogram","boxplot"))    # add radio buttons for chart type
           )
    ),
    column(9, plotOutput("P1"))  # add plot output
  ),
  
  # TASK 4: Add third fluidRow to control how to plot the categorical variables
  fluidRow(
    column(3,
           wellPanel(
             p("Select a categorical variable to view bar chart on the right. Use the check box to view a stacked bar chart to combine the income levels into one graph. "),
             radioButtons("categorical_variable","Category",choices = c("education", "workclass", "sex")),    # add radio buttons for categorical variables
             checkboxInput("is_stacked", "Bars stacked")    # add check box input for stacked bar chart option
           )
    ),
    column(9,  plotOutput("p2"))  # add plot output
  )
) 
# Load libraries
library(shiny)
library(tidyverse)

# Read in data
adult <- read_csv("adult.csv")
# Convert column names to lowercase for convenience 
names(adult) <- tolower(names(adult))

# Define server logic
shinyServer(function(input, output) {
  
  df_country <- reactive({
    adult %>% filter(native_country == input$country)
  })
  
  # TASK 5: Create logic to plot histogram or boxplot
  output$p1 <- renderPlot({
    
     ggplot(df_country(), aes_string(x = input$continuous_variable)) +
        geom_histogram()+  # histogram geom
        labs(y= "Number of P", title = paste("Trend of",input$continuous_variable))+  # labels
        facet_warp(~Prediction) # facet by prediction
  
    
  })
  
  # TASK 6: Create logic to plot faceted bar chart or stacked bar chart
  output$p2 <- renderPlot({
    # Bar chart
    p <- ggplot(df_country(), aes_string(x = input$categorical_variable)) +
      labs(y= "Number of P", title = paste("Trend of",input$categorical_variable)) +  # labels
      theme(axis.text.x= element_text(angle = 45 ),legend.position = "bottom")   # modify theme to change text angle and legend position
    
    if (input$is_stacked) {
      p + geom_bar(aes(fill = prediction))  # add bar geom and use prediction as fill
    }
    else{
      p + 
        geom_bar(aes(fill = input$categorical_variable)) + # add bar geom and use input$categorical_variables as fill 
        facet_wrap(~prediction )  # facet by prediction
    }
  })
  
})

You have

plotOutput("P1")

but

output$p1 <- renderPlot({

Notice that one is a lower case p and the other is an upper case P. Change one of then so that they match.