USB-C connectors only work on target side, not host side?
You are trying to make so-called "legacy assembly". In normal Type-C to Type-C connector the role of host and device are automatically managed over CC line inside the cable. When you are building a legacy cable, legacy connectors/cables don't have CC pins, so the role of a port must be selected with proper resistors INSIDE the cable overmold. Even if a Type-C port has a fixed role as host, it won't output VBUS until it sees a valid signature on CC pins.

Your original cable end with 56k to VBUS indicates that the other end is HOST. Plugging HOST to HOST will result in a problem.

If you want your cable to behave as a device (and take charging function from a Type-C host), you need your cable to pretend to be a device. This is done with 5.1k pull-down on one of CC pins on the Type-C connector end. It should work.