Hello, I work for the MathWorks technical support team. The "getwb" function is only supported by legacy neural network objects. The "SeriesNetwork" object, which is relatively new does not have a documented method for obtaining weights and biases. There is an existing enhancement request in place.
It is possible however, to print the weights and biases associated for each layer.
For example,
net = alexnet
net.Layers(2).Weights %Weights of Convolution layer
net.Layers(2).Bias %Biases of Convolution layer
