Not sufficient permissions to modify Chat plugin settings

I’ve just installed Chat plugin. Then, I’ve activated it in a test blog (not in the multisite network), in order to make some checks and prepare the spanish translation.

I’ve got a @Anywhere key from Twitter in order to use Twitter authentication, but when I’ve tried to put the key in the field, I’ve got this message:

You do not have sufficient permissions to modify unregistered settings for this site

In fact, I get this message if I do any change in plugin settings.

My site: (a test blog).

Is it necessary to activate chat plugin network-wide so that it can work properly?