Unable to connect to March 2018 PBIRS from March 2018 Power BI Desktop - "Server is not reachable"

[messerjc]

Experimenting a bit with the March 2018 PBIRS release in my home environment, and I have a new instance installed on a seperate server, we'll just call it DBSERVER01. I'm able to browse to the main page at http://dbserver01/reports and the web server page at http://dbserver01/reportserver. 

When I try to open a new PBI report in PBI Desktop however, then Save As to the report server, I enter http://dbserver01/reports and only get the following:

I've tried to find additional logging but I've had no success. I suspect an authentication issue, but this message should specify that if that's the case. I'm just in a simple workgroup, no domain, but I have a similarly named account on both systems. If this is authentication, we need this dialoge to prompt for authentication, or give better feedback about what it's not reachable.

[messerjc]

This is definitely looking like an authentication problem. I tried going to the web portal direct again from a different browser with no cached credentials, and sure enough it prompted for a username and password before I could connect. My guess is that PBI Desktop is passing invalid or unknown creds to PBI Report Server. We need the ability to specify a credential set to PBI Report Server I'm thinking...otherwise I think I'm stuck here.