CPANRatings has gone read-only due to low traffic. Existing ratings will still be visible, but it is no longer possible to add new ratings.
In a few months, we expect that MetaCPAN will add review functionality. You can already favorite modules there and see the most popular modules counts.
Why are we doing this? First, we haven't had time to give the site the attention it deserves in quite a while. There are numerous open bugs and feature requests in the GitHub issue tracker. Second, it gets extremely low traffic. Only a few hundred visitors a week, rarely leaving reviews. This will also allow us to shut down a few dependent services and free up resources for other use.
We know that CPANRatings is important to its (few) users and the community, and we look forward to the MetaCPAN replacement. The current site will remain in read-only mode until the replacement is finished.