Ampl finds optimal solution in 0 iteration, but the variables are wrongly set to 0 -

i'm trying solve non-linear problem:

var c; var n;  minimize error: (     (6770924 - (n * c * exp(-c * 1)))^2 +      (3617627 - (n * c * exp(-c * 2)))^2 +      (2344172 - (n * c * exp(-c * 3)))^2 ) / 3; 

when execute code, have success message 0 iteration:

minos 5.51: optimal solution found. 0 iterations, objective 214759264300000 non lin evals: obj = 3 grad = 2. 

but variables 'n' , 'c' set '0'. , using answer bad value function, since nothing subtracted constant values.

if take out 'n' variable function have normal answer, 'c' minimizing function. wrong model described?

thanks in advance.

as mentioned in this post, minos sensitive starting point. example, using 1 starting value n gives better objective value:

ampl: let n := 1; ampl: solve; minos 5.51: optimal solution found. 10 iterations, objective 24439722900 nonlin evals: obj = 34, grad = 33.