Blocked Field

I just added notifications_extra, and some of the fields are working working well. However, in CCK it won't allow my to set subscriptions for tags or CCK fields.

I have it enabled on http://MYSITE.com/admin/messaging/notifications/subscriptions, but it's locked for some reason on the content page and my users can't subscribe.

Is there something that I'm missing? My CCK type is a text field, and each content type has more than one (category, location, education, etc...).

If anyone can offer any insight, thanks!