You need to make sure the USB-C charging device is a USB-PD (Power Delivery) charger and not just a mobile phone Qualcomm Quickcharger power adapter. It won’t charge over the more typical 5V or 9V.
Also, when charging the tablet using the Ravpower USD-PD powerbank, try shutting down the Cube Mix Plus first before charging. It would not charge if I plug in the powerbank while the tablet is turned on. The power light will just flicker on and off for a second but will charge even when I turned on if I do this.
P.S The Cube Mix Plus will charge using 20V when I measured the power draw of the device using a USB-PD power meter.
