Dockerfile for shiny app not working

[pascal28]

I would like to run a shiny application in the cloud. When I am pulling the shiny-verse image without anything in the Dockerfile, the shiny-server default starter app runs. However, when I am building a Dockerfile like this:

FROM rocker/shiny-verse:latest

COPY . /srv/shiny-server/

# expose port
EXPOSE 3838

# run app
# CMD ["/usr/bin/shiny-server"]

Then nothing gets displayed and I am getting a 404 error. uncommenting the last line was not successful either.

My folder structure:

project.Rproj
new_folder/
    ├─ app.R
Dockerfile

My shiny app is the default app

#
# 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)

# Define UI for application that draws a histogram
ui <- fluidPage(

    # Application title
    titlePanel("Old Faithful Geyser Data"),

    # Sidebar with a slider input for number of bins 
    sidebarLayout(
        sidebarPanel(
            sliderInput("bins",
                        "Number of bins:",
                        min = 1,
                        max = 50,
                        value = 30)
        ),

        # Show a plot of the generated distribution
        mainPanel(
           plotOutput("distPlot")
        )
    )
)

# Define server logic required to draw a histogram
server <- function(input, output) {

    output$distPlot <- renderPlot({
        # generate bins based on input$bins from ui.R
        x    <- faithful[, 2]
        bins <- seq(min(x), max(x), length.out = input$bins + 1)

        # draw the histogram with the specified number of bins
        hist(x, breaks = bins, col = 'darkgray', border = 'white')
    })
}

# Run the application 
shinyApp(ui = ui, server = server)

When I run docker locally, http://[::]:3838 displays the default starter app and http://[::]:3838/docker_test/ displays the old geyser app. However, this is not working on a remote server.

However, only having

FROM rocker/shiny-verse:latest

in the Dockerfile works fine and displays he shiny server starter default app. Any help will be appreciated. Thank you.