FirstPublishedDate returns null from news templates in site pages library in a site collection

I have a news template in sitepages in a site collection which I do a "copy" and then publish. However, these news articles managed properties (firstpublisheddate, likescount, comments etc). returns null in a search query. Even if the social bar contains likes or comments it does not show in a search connected to their managed properties. 

In the search schema I have mapped the CP ows_FirstPublishedDate to the FirstPublishedDate MP. Anyone know why these news articles always returns null for every managed property?