I will try to explain my noob-problem a little deeper.
I have a 3-days-render just done as a PNG sequence. I enabled Cryptomatte pass before rendering, but I eventually realized that the png sequence doesn't have Cryptomatte pass.
In other words, I need the Cryptomatte pass, but I can't find a way to not to re-render the whole scene, possibly in another more compositing-oriented format like Open Exr Multilayer, making it possible to load the actual render in the compositor.
Another thing: I know that my render is stored somewhere in cache, where Render Layers load the actual render into the compositor. The problem is that this 3-day-render I've just done, has crashed 2 or 3 times during the whole process, so the Render Layer in my Blender project seems to be empty.
Is there a way to recover my Cryptomatte pass, without re-rendering again the whole scene?
Why is it, every time I close Blender, my Render Layer in the compositor seems empty, losing the Cryptomatte pass?
Thanks all Guglielmo Ruben