Trouble with Newton Raphson Zero Finder

Hey all,

I'm trying to solve an equation with the Newton Raphson Zero Finder, but I can't get a result out of it with this data set. It works with other data sets I've tried, and I've solved this instance of the equation with another program and obtained the result I wanted (about 20), but for some reason I'm having difficulty solving it in Labview. I've attached my VI and the data I'm using. This is what the formula going into the Zero Finder VI is supposed to look like: 
((t*((0.05594*t + 5.2842)*t + 137.37))/(1000*(t+246)))-1.987512E-2
Like I said, I'm getting the result I want when I solve for this specific instance of the formula with another program, so I know that the formula is correct.

Please let me know if you have any insight