Using JupyterNotebook with multiple Python versions

I have installed Python(3.7 and 3.6) because there was some issue with TensorFlow. But, in the venv where Python 3.6 is the default version, Jupyter Notebook throws the following error:

Error 500 Internal Server Error.

The issue gets resolved as soon as I change the python version back to 3.7 but I need to use 3.6 for TensorFlow.

Please Help.