In a new blank scene, I open up the compositor dragging my multilayer OpenEXR sequence in. I can succesfully see a tiniy preview in the Image Node with the correct backdrop, but when I switch from single image to sequence, it disappears.
I attach 2 screenshots. Thank you all for the attention.
EDIT: I can't even use a File Output node, everything is correctly set up but there's no export in the folder (and a very fast render as nothing is calculated).