@igordian Widevine has to be enabled. Go to Brave’s settings → extensions which is brave://settings/extensions. From there you should see a toggle.
Widevine is what is called a DRM (Digital Rights Management) tool that many websites use. It makes it so you can’t record or download protected content. Amazon Prime Video, Hulu, Netflix, and all of those places all use DRM to restrict pirating. If you don’t have a DRM tool, of which Widevine is the most commonly used one, then they wont’ let you view their content.