I use mine all the time, I have noticed though that some needles are harder to thread than others, may be smaller eye size that thethreader doesn't want to fit into.
Sugar, It happened to me a few weeks ago!! I had just replaced the needle, and, yes, the needle wasn't quite up far enough! try it, Love and God's blessings.
I use mine all the time but have found out I will occasionally get a needle that for some reason must be a little off at the eye and the threader doesn't work. Replacing needle always fixes it.
I had a problem in the beginning but I had it adjusted by the dealer and never had another problem. Mine is a Janome Horizon and I habe a Janome 3160 and they both work great.