Solved , problem was the list.celfiles() function.
Now the code is like this:
#ui
###Input CEL files###
box(title ="CEL FILES",
solidHeader = T, status = "info", width = 6,
fileInput("file", "Load CEL files(.CEL)",
multiple = TRUE,
accept = ".CEL",
placeholder = "Please, insert the datapath of CEL files"),
submitButton("Submit")
)
Server side
####Load CEL Files function###########
rawData <- reactive({
validate(
need(input$file != "", "Please Load CEL files")
)
read.celfiles(input$file$datapath)
})