This example uses:
- Neural Network Toolbox
- Computer Vision System Toolbox
Do you have these toolboxes installed on your system? Check the output of the following command to see if they are installed
Also, they mentioned in the documentation:
"The example shows how to train a U-Net network and also provides a pretrained U-Net network. If you choose to train the U-Net network, use of a CUDA-capable NVIDIA™ GPU with compute capability 3.0 or higher is highly recommended (requires Parallel Computing Toolbox™)."
Check for Parallel Computing Toolbox too.
Hope this helps!