Hi,
As per my understanding, you wanted to train a Neural Network using the Regression Learner Toolbox but you are unable to locate the Neural Network model.
In order to use Neural Network model, on the Regression Learner tab, in the Models section, click on the arrow to display all the available models. In the Neural Networks group, click on All Neural Networks. You can read more about this here: Train Regression Neural Networks using Regression Learner App.
If you want to create more complex deep learning networks and have Deep Learning Toolbox, you can try the Deep Network Designer app.
