Did you use your current Discourse email address for all your commits? It doesn’t matter which email you use for authentication on Github. The only thing that matters is the email address that you include in your commits. When you commit as "Foo Bar <foo.bar@example.com>" then you need to use "foo.bar@example.com" here on meta too.
You won’t get the badge as long as your email addresses do not match. But I guess someone from the team could grant to the badge manually. 
Take a look at the plugin source in order to see what’s happening. I highlighted the important parts:
https://github.com/discourse/github_badges/blob/master/plugin.rb#L44-L53
BTW: Didn’t you ask the same a long time ago? 