VS 2017 RTM - Asp.Net Core web app - F5 -> localhost is currently unable to handle this request.

Hi,
I created a new Asp.Net Core Web App.
The app is running fine from dotnet run command or the .exe
I would debug it directly from Visual Studio with F5 in IISExpress or the .exe 

When I press F5,  a small Chrome page opens but remains empty.

When I press Ctrl+F5, I get "localhost is currently unable to handle this request."

Any help would be great
txs

-Vince