I am doing deep learning using a multi-layer perceptron for regression. The loss curve turns flat in the third epoch however accuracy curve remains flat at the beginning. I wonder whether this makes sense.

I am doing deep learning using a multi-layer perceptron for regression. The loss curve turns flat in the third epoch however accuracy curve remains flat at the beginning. I wonder whether this makes sense.

Since you didn't provide the code, it would be harder to narrow down what is the problem. Being said, here are some pointers that might help you see what is the problem:
validation_split in fit function, then keras will only take the last percentage of your training set and will keep it the same for all epochs. link]).Hope these pointers help you with your problem.