Issue with Cinemachine

Hi there!
I am having a issue that is confusing me a lot:
I am creating a custom viewer for my company, and i wanted to include some cameras to focus on some functionalities like a general view of the model (like an orbital track or a main tour). The issue comes when I import any CM virtual cam in to the scene, I use to deactivate the other cameras in the scene to see how i am setting up the new one. The case is that the preview turns black and a message appears saying "Display 1 no cameras rendering", and I don´t understand why (is not like a standard camera that you have to choose the target display)

 

I have already include other Cine Machine Cameras to the scene to inspect some elements and worked fine, Idk why i cant add this one.

 

Yep, like half an hour later I realized that I need the cinemachine brain script attached to my main camera and now works fine!
Ty so much for the reply!