Many speed controls have a safty feature that requires you to pull the throttle stick all the way down and hold it there for several seconds (usually 3-5, which doesn't sound like much, but is actually quite a while). Just wiggleing the stick won't do it. I'm guessing you aren't holding the stick all the way down long enough at first, then get frustrated and set the TX down for a moment, or pause to check something like a connector, and pick it back up to find it suddenly working. That pause gave it the delay it was looking for. Don't sweat it, this is pretty much what I did the first time I hooked up my electric before reading the instructions.