I have epub with KDP and it works fine with kindle app.
But on kindle paperwhite it says the
“unavailable for download”
"The item not compatible with this device’
What should I do for the epub to be compatible with kindle paperwhite.
You will need to convert the EPUB file to a kindle compatible file format (mobi or azw3). You should be able to do this with free software like Calibre or Kindle Previewer.