Sounds like you have everything connected properly. All of the connections on the D5 Next are detailed in the User and Installation Manual. DOWNLOAD LINK The D5 Next is SATA powered so you MUST connect a SATA power cable. The 4-pin Fan header between the RGBpx/Aquabus header and USB header can function as a PWM fan port (25W max power) or a Flow Sensor input. Which cable you need to connect a flow sensor to this header depends on which flow sensor you have. Connecting a PWM fan or a flow sensor are both optional. The RGBpx port does not need to be connected to the mobo. You only need to connect the USB cable to a USB2.0 header on the mobo. The RGBpx port is controlled by the Aquasuite software.

Note: The D5 Next has a "Virtual Flow Sensor" feature that attempts to calculate flow rate based on several parameters. Their is a calibration procedure described on pages 19-20 of the User and Installation Manual. Even after calibration, the Virtual Flow Sensor is not very accurate and is only intended as a flow / no flow indicator. If you want to accurately measure flow rate, you should install a real flow sensor like the High Flow Next, High Flow 2, or High Flow LT.