Lasso regularization problem

Hi… I need to solve this minimization problem in one part of my code…
min_x {torch.norm(x_n - x,2)+lambda1*torch.norm(y_n - Ax,2)}
I used cvxpy library for this problem,I coded this like bellow:

x_es = cp.Variable(64)
lambda1 = cp.Parameter(nonneg=True)
lambda2 = cp.Parameter(nonneg=True)
problem = cp.Problem(cp.Minimize(objective_fn(x,x_n,y_n,A,lambda1,lambda2)))

I got this error during Ax part:

matmul: Input operand 1 does not have enough dimensions (has 0, gufunc core with signature (n?,k),(k,m?)->(n?,m?) requires 1)

how could I can solve that minimization? I want to solve this part without training…