How to load a saved model in TensorFlow?
The TensorFlow documentation for tf.saved_model.load might help: 


  SavedModels from tf.estimator.Estimator or 1.x SavedModel APIs have a
  flat graph instead of tf.function objects. These SavedModels will have
  functions corresponding to their signatures in the .signatures
  attribute, but also have a .prune method which allows you to extract
  functions for new subgraphs. This is equivalent to importing the
  SavedModel and naming feeds and fetches in a Session from TensorFlow
  1.x.


You might have to use deprecated v1 api call 
https://www.tensorflow.org/api_docs/python/tf/compat/v1/saved_model/load