I’m not sure what eaxctly is causing that. Often it’s because there is a for in the path. Did you copy or otherwise edit the helix after creating it?
that’s the number of sides or edge segments used per turn of the helix. Similar to the number of sides in a circle.
Thank you!
As I said, I don’t know what I did. I might have edited it. I’ve decided to delete the helix and try yet again but paying very close attention to my actions as I proceed.
Sides/Turn makes sense now that you told me what it is. 
UPDATE:
I’ve tried to get the Follow Me Tool to work without success. I’ve tried with the drawn helix as a group and exploded (because it is a group by default). I’ve tried with the circle attached to one end with face reversed and not reversed. I’ve even tried making it a component and editing it by adding the circle to be extruded along the helix line while having the face reversed and not reversed. In each instance I got the same message saying that the path did not appear to be valid after clicking with the Follow Me Tool.
I don’t know what else to try. I have been unsuccessful, so far, in finding any useful tutorial in using the Helix function within the Curve Maker extension.
The error is fairly generic. It seems to be failing because the coil has too many segments for it to cope with.
Thanks, Box!
I’ll experiment with that.
You may find a combination of less segments per turn of the helix and less segments in the circle will give you the full height and a smooth enough result.
That worked a charm. I reduced the number of coils to 26 and the number of sides per turn to 24 and Follow Me worked.
Thanks, guys!