Is your MX Master the "mac" version? The reason I ask is because my 3s came with a USB-A dongle (which I prefer instead of Bluetooth). I've never used its charging cable, so I don't remember whether it was c-c or c-a. It also didn't have a C-A adapter provided, so if you want to use the dongle and only have usb-c ports available, you have to supply your own.