Today I received a letter from Imgur
Hi Imgur API user,
We’re contacting you with an important update to the Imgur API. Starting on December 1, 2016, Imgur messaging will no longer be available in the API. Your client will be able to access older archived messages in read-only mode for a short time, but no new messages will be sent or received.
What does it mean that the plugin doesn't work after 1 December?