Curve Fitting

I am trying to fit data to a logistic curve as shown in the attached file. However, "lgsfit" will not converge to an acceptable solution. When I plot the function that is returned, it is a very poor fit, no fit at all actually. The data fits the form of a logistic curve very well, as seen in the plot in the attached file. The solution returned is very sensitive to the guess values.

Does anyone have a suggestion?