I had the same error and tried installing and uninstalling. In the end, I found that the library was not actually installed correctly.
I went through each library in my:
C:\Users\MyName\AppData\Local\Packages\PythonSoftwareFoundation.Python.3.8_qbz5n2kfra8p0\LocalCache\local-packages\Python38\site-packages\
I tracked down the file in within the site-packages in Keras, which was calling from the Tensorflow library, which was calling from another folder. I found the final folder had the get_session(), but this was not being called in. When I checked the directory, I found that get_session wasn't being loaded in. Within the file directory /tensorflow/keras/backend.py it was importing everything, but missed out the get_session.
To fix this I added this line:
from tensorflow.python.keras.backend import get_session
Then saved it. The next time I ran my code it was fine.
I gave the same answer for this page How to fix ' module 'keras.backend.tensorflow_backend' has no attribute '_is_tf_1''