had the same issue using sydney template and the following plugins:
– Black Studio TinyMCE Widget
– Page Builder by SiteOrigin
– SiteOrigin Widgets Bundle
AND
– Responsive Background Image
as soon as I deactivate “Responsive Background Image plugin” then it works fine; when its activated, then it doesn’t work
hope this helps …
btw: I used german as default language; changed back to english and had the same problem…