下载CSV按钮不显示在Shiny仪表板中

Question

在闪亮的仪表板上呈现数据表时，下载CSV / Excel按钮未显示。有人可以告诉我这是怎么回事吗？

这是我的代码

Server.R

shinyServer(function(input, output, session) {


  widget = datatable(DT, filter = list(position = "top"), options = list(pageLength = 10, scrollX = TRUE), 
                     rownames = FALSE, style = "bootstrap",
                  extensions = 'Buttons'
                , options = list( 
                  dom = "Bfrtip"
                  , buttons = 
                    list("copy", list(
                      extend = "collection"
                      , buttons = c("csv", "excel", "pdf")
                      , text = "Download" ) %>% formatCurrency(4:33, "", interval = 3, mark = ",", digits = 0)

output$table<- renderDataTable(widget)