I am a c# developper working on an aspnetcore application for a customer. I have developped a REST OData service (controller) in this application with basic authentication support, and it is working fine in HTTP mode (used for development and testing purpose), from the browser (Firefox) and from PowerBI, both with authentication support. However, whenever I try to use it with HTTPS, it works fine from the browser with authentication but there is a 404 error from PowerBI. I have activated traces in diagnostics options and also made traces with Wireshark (attached). Looking at the PowerBI Traces (attached), I can see that there is a switch between https to http between the call Engine.IO.OData.GetResponseStream and Engine.IO.Data.Request in MashupContainer container code (?!!!), hence the 404 error: there is no odata service on 80 port on my server, it is on 443 with TLS. Wireshark also shows that packets are sent over HTTP with credentials in clear text.
Whatever I missed in the configuration , IMHO it looks like a bug, plus a serious concern for security: credentials should never be sent on the wire without encryption in case of end-user configuration error!