syms 0-by-1

When I hit run, the commend window returns empty sym: 0-by-1. Can someone help me to spot the error in this code? Thank you!

clc,clear

Ts = 293.15; %ambient temp

Tmelt = 923; % melting temp

I = 1.5; %current

rho = 2.4E-8; %resistivity

syms r; % radius

L = 0.1;

k=15;

eps = 0.65;

sig = 5.6703E-8;

Tavg = 512.86;

hr = eps*sig*(Tavg^2+Ts^2)*(Tavg+Ts);%10.367

c = rho*I^2/(k*r^4*pi^2);

m2 = hr*pi*2*r/(k*pi*r^2);

m = sqrt(m2);

N = c/m2;

eqn = Ts+N*(1-(cosh(-0.5*m*L)/cosh(0.5*m*L)))==Tmelt;

solve (eqn,r)