In Distances, a collection of points (even if the points are one dimensional) is given as a matrix, not a vector. So either create it as a matrix or use the adjoint operator ' to give it an extra dimension.
julia> pairwise(Euclidean(), cc'; dims=2)
4×4 Array{Float64,2}:
0.0 2.0 4.0 6.0
2.0 0.0 2.0 4.0
4.0 2.0 0.0 2.0
6.0 4.0 2.0 0.0