Devices with USB-C connectors on them won't connect via double USB-C cables to PC or power

[Android Central Question]

I have a Samsung Galaxy Tab S4, which is powered via a USB-C port on the tablet. My PC has a USC-C port on it and I have several chargers that have USB-C outs. The Tab will not connect or power if the cable is double ended USB-C, only if it is USB-A to USB-C. Cords checked and confirmed good on multiple other devices (pixel 2, moto phones, etc.) Anyone have any idea what is going on?

 

[B. Diddy]

Some powerbanks only use the USB-C port for input (i.e., when you have to charge up the powerbank itself). Are you certain yours is designed to also charge devices from the USB-C port?