That’s funny. I see a copy of my message in one of your messages above, and it includes the link to repro the problem. It’s not directly to the 404 page, but rather to a link that produces a 404, and since the plugin doesn’t manage to redirect this one automatically, I at least want it to list the closest matches, which will probably include the right one.
Here is the link again: https://blog.nerdbank.net/2009/10/vs2008-project-template-for-openid-and.html
Regarding your second post where you see a discovery info does not match assertion info error, the discovered info says the OP endpoint is:
http://pupeno.com/openid/server
But your WordPress provider is asserting this OP endpoint:
http://pupeno.com/index.php/openid/server
The discovered and asserted endpoints must be identical. So this is a bug either in WordPress or your configuration of it.