using actionButton + insertUI in R shiny modules to create multiple inputs

There are some errors you need to fix:

1. to use modules, you must have IDs for both UI and server. For each pair, they must have the same ID.
2. For ids in module UI, you must use namespace NS.
3. For insertUI, default is insert into the selector, apparently, you don't want to insert inside a button, you need to add after the button, so you need have where argument, please read the help file of this function.

You should read more about shiny modules standards

Here is the working code:

library(shiny)

importExceldataUI <- function(id){
    ns <- NS(id)
    tagList(
        tags$div(
            HTML(paste0("<b>", "Enter Your Data Here"))
        ),
        tags$div(
            fileInput(inputId = ns("ImportExcelFile"),
                      label = "Excel File",
                      multiple=FALSE),
            style = "display:inline-block; vertical-align:top"
        ),# end of tags$div for fileInput ImportExcelFile
        
        tags$div(
            textInput(inputId = ns("ExcelSheetName"),
                      label = "Sheet",
                      value="Data"),
            style = "display:inline-block; vertical-align:top"
        ),#end of tags$Div for texinput-ExcelSheetName
        
        tags$div(
            textInput(inputId = ns("ExcelSheetRange"),
                      label = "Range",
                      value = "C5:BN1000"),
            style = "display:inline-block"
        )#end of tags$div for textInput - sheetrange
    )
}


importExceldataServer <- function(id){
    moduleServer(id, function(input, output, session){
        observeEvent(input$ImportExcelFile, {
            req(input$ImportExcelFile)
            print(input$ImportExcelFile$datapath)
        })
    })  
}

importExceldataApp <- function(){
    ui <- fluidPage(
        mainPanel(
            actionButton(inputId = "AddExcelDataButton", label = "Click here to add Excel Data"),
        )#emd pf mainpanel
    )
    
    server <- function(input, output, session){
        observeEvent(input$AddExcelDataButton, {
            insertUI(selector = "#AddExcelDataButton", where = "afterEnd",
                     ui = importExceldataUI(paste0("file",input$AddExcelDataButton))) 
            importExceldataServer(paste0("file",input$AddExcelDataButton))
        })#end of observeEvent
        
    }
    
    shinyApp(ui, server)
}


importExceldataApp()

So to read the path of uploaded file, just use input$ImportExcelFile$datapath, datapath is the file location. Here in my code, I just print it out, you can do other things.