Problem to create gerber files with inner layer

Hi.

I have problem with 13.0.2 to generate gerber files of a pcb with 4 layers.
I see correctly the layers in the editor, and the setting parameters seem correct.

But when I see the generated gerber files with a Gerber file viewer (like jlcpcb) the inner layers are showed like Vcut layer.

How can I solve this issue?

Thanls in advance.