On the nexus nx2 multi make sure cal code C73 is off. It is BSP and off=nexus speed transducer, on=NMEA0183 speed source. C74, C75 and C76 should also be OFF to get Nexus transducer depth, compass and wind. You can also see if your speed transducer is likely working by checking the lower line on the multi plus page and it shows water temp. These are server settings and affect ALL displays.
Also check cal code C95 and make sure SOG=off. This is a display code and only affects one display so each display may have to be set C95=off to see paddle wheel speed on all digital display