File Upload Button Wont Show on Order Detail Page

Hi

Thanks for your plugin. I have installed the plugin and set the status:
https://screencast.com/t/CvggToAK

and enabled upload on product page(screenshot):
https://screencast.com/t/wo30Bm6k

but when I go to order detail page there is no button to upload the files, please check screenshots:
https://screencast.com/t/yBD9LSllLY
https://screencast.com/t/fctp4f3CUYsU

would you please let me know why the File upload button is not showing?
I am using version 0.3.5 and my woocommerce version is 2.1.12

Thanks for your help

https://www.ads-software.com/plugins/woocommerce-upload-my-file/