Child theme with Vantage premium not working properly

Hello,

I’m using a child theme based on Vantage Premium and I have several issues about it:
– the icons are not displayed: the home icon in menu, back to top icon and all the icons in circle icon widgets, etc. Instead there is a strange rectangular character
– the visual css editor doesn’t work at all
– the Customize option (under Appearance) doesn’t work properly: in the right pane, I only see the login page, asking again and again to login, with no results.

I have tried to use Vantage without a child theme, it works perfectly well.
Since I’m only at the start of the site, I have very few plugins installed: only Akismet, All in One SEO and WP supercache, and of course Page Builder and SiteOrigin CSS.

Thank you for your help to solve the situation.
CHristine