Solving an equation multiple times using a for loop

Hello,

I am trying to solve the following equation for time (t) using different air temperatures. Matlab says that the solution is 0*1 empty double column vector!

Thank you for your help.

clear all
clc
x=1
for T_a_amb=[270.928:0.01:272.594]    %ambient air temperature
    syms t
    a = -4/(T_a_amb-277); 
    b = 5.948e-5;
    c = 0.00771;
    eqn = 1-(exp(b*t)*(1-erf(c*sqrt(t)))) - a== 0; %
    solution = double(vpasolve(eqn,t,[0,1]))
    solmate(x,1) = T_a_amb;
    solmat(x,2) = solution;
    x = x+1
end

[Bob Thompson]

Is the vpasolve coming up with a set of answers? That would be my first thought to check.