When trying to transfer files through Web browser (HTML5), “Upload” or “Download” tab does not appear in the “Transfer Files” panel.

In case of Safari on iOS and Safari 8, “Upload” and “Download” are not supported.
In case of Safari 9 and later version, “Download” is not supported.
(Refer to REMOTE ACCESS – On Web browser (HTML5) – [File Transfer])
Please use another web browser to transfer files.