The red wire (which has a heat-shrink cap) was for optional use in the 5000 series, and is not supposed to be used at all for the TED Pro. I have no idea why it is still there, but I suppose that there may be special circumstances under which Tech support may tell you to connect it. If your MTU is not flashing after you have connected Black to Live and White to Neutral, it is almost certainly defective (but check with a voltmeter that you haven't got a faulty circuit breaker - does very occasionally happen).