How can I find out where is the problem came with my installation on caddy?

my server run on a new debian9 &php7.0&mariaDB&Caddy,which is using the configuration from the Caddy Docs. the phpMyAdmin is running good,but not the Nextcloud.
After installtion , I can sign in NextCloud(i would loved to call NC instead).and then ,the main page shows me an alart with chinese “操作被禁止”----“operation is forbidden”.sth like that.
here is sth what I tried.
chmod -r 770 for nextcloud WWW &Data dir
chown for NC www&Data dir.
The Caddyfile:

almost the same
and the main page is not showing anything!
include the DEMO files!