If you are on Windows 8.1, and you are attempting to run an ASP.NET Core 3.1 Web Application, you’ll have run into the dreaded ERR_HTTP2_INADEQUATE_TRANSPORT_SECURITY error message. Here’s the workaround. Add this to your appsettings.Development.json file.
"Kestrel": { "EndpointDefaults": { "Protocols": "Http1" } }