Process File element does not read custom attachment object

Hi Creatio Community

I have created a custom attachment object which is sitting in a detail.

While trying to use the "Process File" element in a business process, I am unable to see that "custom attachment object" in the "Which object to receive file from?" dropdown list.

I need to trigger a business process whenever a new file is added in that custom attachment object, and then use that file as an email attachment in the Send email element.

Can you help me figure out how can I read the files present in that custom attachment object in a business process?

Thank You.