F5 failed start start function app in Azure Cloud Shell

I was following the learning path on Microsoft's website for the Azure Developer Exam. In the exercise to learn about SignalR, there is a step to press F5 to start the function app from Azure Cloud Shell. However, nothing happens. And there is no option in the editor itself to start debugging. I tried this step on both a Mac and a windows PC, neither work. Any suggestion on how to get pass this step? Any help is appreciated.