External strorge activation -> blank page

I just setup a fresh installation of [Nextcloud 13.0.0 on ubuntu 16.04 using an EC2 instance of amazon, and try to activate the external storage.
Using applications parameters I have activate the external storage support.
When accessing the parameters I see on the left menu the “external storage” item, but when I chose this item, the main page (on the right) briefly display some items on the top, then display a white page, menu on the left stay enable.