It may not be your Opus, but your battery. Check your battery with a voltmeter when it's cold and find out what it reads. If it's under a certain voltage, the Opus will completely shut down to avoid draining the battery.
Even if this is the case, though, it should power on within a few seconds of your engine starting (and your alternator taking the battery voltage up to 14-16V or so)
My opus has reliably worked when it was 5 deg. Farenheight outside, so if it's not your battery voltage going wonky with the weather, then you probably should get in touch with opus about it!