This is what I just did and seems to work.
On the file README.rst on line 40 it says:
#. navigate to your site and check your database to make sure the ^userbadges table was created
There was no table there, and the memory error was preventing the plugin to create the table.
PHP Fatal error: Allowed memory size of 134217728 bytes exhausted (tried to allocate 12956 bytes) in [snip]\qa-plugin\q2a-badges-master\qa-badge-admin.php on line 17
So I commented out the line 17 on qa-badge-admin.php like this:
//$slug = preg_replace('/badge_(.+)_[^_]+/',"$1",$option);
And then went to www.mysite/admin/plugins, then I checked and the table was created, after that I removed the comment from the line like this:
$slug = preg_replace('/badge_(.+)_[^_]+/',"$1",$option);
And it is working now.
Hope this helps others with the same problem.
If you use this procedure to activate the plugin, please read this other question: