search results problems

Hi, I’m using clean retina as my theme.
I created a custom type, also some custom fields and finally some custom Taxonomies.
One of the taxonomies is named isbn for example, when I search for that specific isbn code it doesn’t show any results which means that it’s not recognizing any of the custom taxonomies or fields that I have created.

Could you please tell me how to fix this? Maybe which lines to add the the search.php file or anything like that?

I also would like to change how the search results look, for example showing the feature image of the blogs, etc.

Thanks in advance for your help!