I have googled and found the similar issue https://github.com/plotly/dash/issues/257 in another project, so it looks like Flask==1.0.2 creates the problem. We will have to downgrade the Flask back to 0.12.2
@Fahar meanwhile can you please uninstall the Flask and reinstall the v0.12.2. Please follow the commands that I did on my windows machine (Refer attached screenshot)