Offizieller Kommentar
@Rick > Congrats on the XDJ-RX purchase -- I think there's an easy solution for you.
The SX EQ settings were configured within Serato DJ and chances are you never thought about them / touched them. The XDJ-RX has two ranges, and that's indicated by the -26/-∞ markings beside the knob. It's either a 26dB cut, or a full kill - and chances are yours is set to a full kill.
Press and hold the MENU/UTILITY button and scroll down to EQ CURVE, press the knob, change the setting from ISOLATER (yes, complete with typo), to EQ... and enjoy! :)