It's working perfectly here...
I have an SM58 running through my BArp. With the preamp's range set to 100X (and with the preamp's slider fully up), it triggers the envelope follower quite strongly, output from pre-amp to an audio in of the VCF has good levels, and with a connection straight to the BArp's Mix IN, gives a strong signal on vocals. With range set to 1000X, the preamp's slider needs to be below 50% for it not to distort.
I tried it just then, to be sure...
Could it be the pin-outs on your mic cable plug? If you're using XLR or TRS with a 3.5mm adapter, you'll need a Y cable, and just take a signal from the ring.