WordPress Themes, Plugins and HTML Templates › Forums › Arcane WordPress Theme › Blog is not a known valid target type for the mainContentOfPage property. › Re: Blog is not a known valid target type for the mainContentOfPage property.
Arcane 1.1 is released which fixed the Schema Markup errors and several other improvements.
You may be interest to read the full thread – https://designorbital.com/community/threads/arcane-1-1-released.390/
Go to your members area and download Arcane 1.1