Keras model producing same output
It happens often, that some model only predicts one class. The reason usually is, that the model is unable to distinguish the two classes well, and resorts to one (often the majority) class.
With your data, you may have a hard time to fit a NN with reasonable results. I suggest you check boosting which usually works okay with small data. Make sure you tune parameters well.
Here is an application of lightgbm to the iris data.
You could also check Logit with L1 regularization.