Why does Microsoft Edge open some local websites, but not others, where the domain name is routed to in hosts file

Your network can block loopback as a security measure in Windows 10. Open a command prompt as administrator, and run this to exempt Edge from a loopback: CheckNetIsolation LoopbackExempt -a -n=”Microsoft.MicrosoftEdge_8wekyb3d8bbwe” (Microsoft.MicrosoftEdge_8wekyb3d8bbwe is the identifier for the Edge app) There’s a blog post here giving more detail: https://blogs.msdn.microsoft.com/msgulfcommunity/2015/07/01/how-to-debug-localhost-on-microsoft-edge/