Fitted curve disappeared (Curve fitting toolbox)

Hello,

using curve fitting tool, my fitted curve disappeared as the photo shows.

My equestion is (1/2*(erfc((0.16-0.5*t)/(2*sqrt(D*t)))+exp(33.67*0.16/D)*erfc((0.16+0.5*t)/(2*sqrt(D*t))))) and my inuputs are :

t= [0 15 40 60 75 90 105 120 150 180 195 210 225 243 270 300 330 360 390 420 480 540 600 720 900 1200 1500 1860]

C=[0 0.00789470000000000 0.010000000000000 0.00526320000000000 0.0102632000000000 0.0105263000000000 0.0157895000000000 0.0157895000000000 0.0157895000000000 0.100000000000000 0.342105300000000 0.605263200000000 0.792105300000000 0.868421100000000 0.900000000000000 0.900000000000000 0.921052600000000 0.947368400000000 0.947368400000000 0.947368400000000 0.947368400000000 0.947368400000000 0.947368400000000 0.947368400000000 0.947368400000000 0.947368400000000 0.947368400000000 0.947368400000000]

T=t./86400;

disp(T);

Any idea ?

Thank you