Dear Carlos,
I'm sorry but I do not know enough about the plugin to say why. Unless I have guest access to your site to see what is going on and a copy of your One Topic code to compare with the distributed version.
I suggest that you double check that all the files have copied correctly from the download to your site. It was an issue with my format a few weeks ago with another user.
If all is the same, I would suggest contacting the developer with the contact in the Plugins Database.
Cheers,
Gareth