Connect HCI to ERP on-premise

Hello!
I am integrating SAP ERP with SAP C4C via CPI (HCI).

Iit is working just from ERP to C4C,

from HCI to ERP im getting errors, is it necessary to use cloud connector?? what is the most simple way to do it?
i have just tryed wiht hostname and port that I see en tcode SMICM -->Services