You are not passing your datasets to your training job when starting it using the sagemaker SDK.
Currently, you have
huggingface_estimator.fit() # put this inside fit if using train.py: {'train': training_input_path, 'test': test_input_path}

=> Saying to sagemaker you are not passing data from s3.
You need to change this to
huggingface_estimator.fit({'train': training_input_path, 'test': test_input_path})