Use text-mode in editor and paste it as a non formatted text.
Also make sure that plugin is enabled.
Thanks George for your help, but it does not work yet.
Maybe a conflict with theme?
Thanks!
Probably. In your case, I’d verify it with the following way:
1) Revert to twenty eleven them (or a similar default one) and retry.
2) Deactivate all plugins and retry.
If in any of the above cases, shortcode starts working again, you should activate theme and retry to verify the conflict. If it continues working, you will need to do the same with your plugins, one by one, until you find the conflicting one.
Once the issue is verified, you’ll have to investigate the conflict (usually done by gathering information and parsing them to the developer of the theme/plugin that conflicts).
Yes, it’s a conflict with a particular section of theme.
So your plugin works right!
I’m gonna ask to the author of the theme.
Thank you so much!