Adding another module shouldn’t affect the coarse tuning, so odds are something else is broken. The VCO frequency is controlled by the sum of two (or more) voltages. If you have a multimeter, you can measure the voltages in circuit, see the annotations here:
Measure between 0V/GND and the 100k resistors (the points marked CV and TUNE CV). The voltage on the TUNE CV should change if you tweak the tuning knob, and the sum should be well over 5 V for things to be audible (see the chart further down). If this isn’t the case, check the wiring.