Why does "Process File" process element only shows some of the objects?

Hi Community,

We've this situation where we need to get a specific attachment from a specific object. In order to do that we've created a new process that is using the "Process File" process element to get the Attachment, as you can see bellow:

The problem is, the "Process File" element only shows the default objects files. How can I receive the attachments from my custom objects through this element?

Note: Both custom object and process are on the same package.

Thanks in advance.

Best Regards,

Pedro Pinheiro