To give another deviant a direct link to this FAQ answer, use the following code in your comment or forum post:
I paid for a Premium Membership and it said my Premium Membership is activated but I do not have all my features yet. Why is this?
This can happen for a few reasons;
1.) Some Premium Membership features need to be enabled under your deviantART 'Settings' or 'Profile' pages. Please double check that you have done so.
2.) Some features are not retroactive and will not begin right away, for example this is the case with the "Recent Visitors" widget and will require you receive a visitor with their status not set to invisible before it begins registering visitors.