Neural Network example code not working?

Hello I am try to test below this example: https://www.mathworks.com/help/nnet/examples/transfer-learning-using-convolutional-neural-networks.html My MATLAB version is R2016a.

The "DigitDataset" file not found in my directory. I changed directory to digittest_dataset, this case have not error. But ImageDatastore struct have empty elements.

Thank you for your advice.