There is no way to know for sure without examining the defective lens assembly, but…
I know of cases where the internal iris has stuck. If it sticks in the “open” position, the camera will appear to work, but may have washed out pictures/videos. If stuck in the “closed” position, you will see black in both cases. In your case, what appears to be nothing showing on the screen may be a stuck iris in the closed position. Since these lens assemblies are often sealed, there is no way to actually “fix” them unless you have access to a clean room.
Hope this helps,
Dan