Start export button does nothing on XWiki 15.10.10

Steps to reproduce :

• Install the extension on a 15.10.10 instance
• Add a livedata table on a page (first example provided in https://extensions.xwiki.org/xwiki/bin/view/Extension/Live%20Data%20Macro/ documentation)
• Click on the "Export…" item in the menu at the top right of the Live Data instance, then click on "start export"

Expected behaviour : export starts, then allowing to download the export

Actual behaviour : nothing happens