Why does the dot product between a matrix and a vector not work?

Question

Executing this code:

f[x_] := x
n := 4
nb1 := CoefficientList[
  Series[Integrate[Integrate[f[x], {x, 0, x}], x], {x, 0, 5}], x, n]
nb1
to := Table[
    CoefficientList[Expand[(t + 1)^k - (t)^k], t, n], {k, 1, n}] // 
   Transpose // MatrixForm
to
Dot[to, Transpose[{nb1}]] 

I get the following final output:

Why the dot product is not evaluated here?