Uploading and downloading with reactive values in shiny

Question

I'm using fileInput to upload a file that is needed to be edited and then creating a workbook, which needs to be downloaded. Getting the error: "Operation not allowed without an active reactive context. You tried to do something that can only be done from inside a reactive expression or observer" I updated the code by the answers from other question.

Why do I still get this error?

server <- function(input, output) {
 
mydata = reactive({
  req(input$dat)
  read_excel(input$dat$datapath, col_names = FALSE)
  })
  
mydat <- reactive({
  mydata <- mydata()
  mydata <- mydata[-(1:2),]
    names(mydata) <- mydata[1,]
    mydata <- mydata[-1,]
    mydata <- mydata[,-1]
    mydata <- data.frame(mydata)
})

func <- function(d){
    x <- na.omit(as.numeric(d))
    mean <- mean(as.numeric(x), na.rm=T)
    sd <-   sd(as.numeric(x), na.rm=T)
    Tmin <- mean - (3*sd)
    Tmax <- mean + (3*sd)
    return(x[which(x < Tmin | x > Tmax)])
  }
  
red_style <- createStyle(fgFill="#FF0000") 
out <- reactive({apply(mydat(), 1, func)})
    
w <- reactive({
    w <- createWorkbook()
    addWorksheet(w, sheetName="Data")
    writeData(w, sheet="Data", x=mydat())
    })
    
seq <- 1:nrow(mydat())
for(i in seq){
      if(length(func(mydat()[i,]))>0) {
        yB <- as.matrix(which(str_extract(mydat()[i,3:ncol(mydat())], '\\d+.\\d{2}') %in% 
                                str_extract(as.character(out()[[i]]), '\\d+.\\d{2}'), arr.ind=TRUE))
        yB <- yB + 2
        addStyle(w(), sheet="Data", style = red_style,  cols=yB, rows=i+1)
      }
    }

output$download <- downloadHandler(
    filename = function() {
      paste0("Data-", Sys.Date(), ".xlsx")
    }, 
    content = function(file){
      saveWorkbook(w(), file, overwrite=TRUE)
    }
  )}