Thread Subject: optknt

I have a nondecreasing sequence of 234 points (parameters) and I want to make knot vector from those points using optknt. But I get this error mesage:

??? Error using ==> optknt at 58
Damped Newton iteration failed to converge.

I've tried this
>>optknt(avg_knots, 4, 50)
but I still get the same message.

Why do I always get this message? What does it message mean and what's wrong with my parameters?

Thank you
Didi