I can't get my external microphone to work properly with my camcorder?

I have a Canon HF R200 Camcorder and a Sennheiser freePORT presentation wireless microphone system. I connected the camera to the freePORT receiver unit via stereo XLR to 3.5mm jack. The camcorder is picking up sound from the microphone but it sounds muffled and like a robot is talking. I've tried adjusting the gain on the receiver unit, and tried both the line and mic settings on the camcorder. Any suggestions?