Today, I updated my Blackbird theme to PRO, and the Testimonials section of the home page is not working. The defaults were working. But when I changed the testimonial text, the "Client Testimonials" title is visible but the actual testimonials are not. When I erased the custom testimonials, the defaults are still invisible.
The problem is occurring due to any one of the plugin you are using, Deactivate all plugins one by one and checkout which plugin creating this problem.