I was helping to get it working on another Windows 10 box with VS 2015 when we got the error:
"The Process ID cannot be found for .NET Core exe".
Works fine on my Windows 8.1 box.
If we run .NET Core from the command line and then ran the project, it loaded but then localhost refused the connection.
So Mr. Google to the rescue and the vast majority of the suggestions were along the lines of:
"For me the problem was solved by closing down Visual Studio, deleting
and starting Visual Studio again"
That didn't help and neither did a whole lot of others.
Then I came across a reference along the lines of localhost certificates that aren't trusted for SSL.
And some bells started ringing because I hate IIS Express and don't use it but the Windows 10 machine did not have IIS installed so was running IIS Express by default.
(I always battle with IIS Express and SSL).
And the B2C sample uses https://localhost.
You need to trust the IIS Express self-signed certificate as per this post.
That fixed the problem.
How a trusted certificate issue caused an error message regarding a process ID is another issue entirely :-)