The twin-function knobs, "VCO1 < VCO3 > VCO2", "VCF1 < VCO3 > VCF2" and "VCO1 < Noise > VCF2", need to be engaged a little bit for modulation to take effect. When these are at their middle position, their function is switched off. They're not actually bipolar parameters like e.g. the coarse tune knobs. Instead they're 2 different parameters sharing a knob. In the voice circuitry there's actual switches to engage one of the two functions, and they're off when the knobs are in the middle.
So, if you e.g. turn "VCO1 < VCO3 > VCO2" a little in the direction of VCO1, then the macro knob will work. You only need to turn it ever so slightly, and the macro knob will give you control of its full range if its Mod Amount is at +/- 99 (the same goes for any other modulator you care to assign in the matrix for the twin-function knobs).
There's a small dead band between the engaged position and the position where the VCO1 > VCO3 FM actually takes effect. This means you can engage twin-function knobs, ready to take modulation from the matrix and still have no FM by default. You can hear when the knob is at the exact point when it engages as a slight jolt in the VCO frequency. So if you turn it no further than that, it's engaged, but with a value of 0.
If this works as describe above, your synth is in good health.
Ed: reworded for clarity
