can't reach JupyterHub

Hello everyone, I've just started using AWS services and more generally I'm a complete beginner when it comes to using the cloud. For the purposes of my training, I need to create a cluster with EMR by activating JupyterHub but when I want to access the notebook, I get the error "Spawn failed: Server at http://127.0.0.1:54791/user/jovyan/ didn't respond in 30 seconds" as you can see on the screenshot. I'm on Windows and I've followed the instructions provided by Amazon to the letter to activate the internet connection using putty and then FoxyProxy for Firefox.

Thank you in advance for your answers.