The Behance Publish Service plug-in has been removed as of Illustrator CC 2015.3.1.

Workaround

You can export artboards from Illustrator and upload them directly to your profile on the Behance website, either as a Work In Progress asset or a Project.

1. From Illustrator, export the artboard(s) you’d like to share to your local hard drive.
2. Log in to https://www.behance.net/ with your Adobe ID.
3. Click My Portfolio to see active Projects and Work In Progress assets.
4. Click Add Work to upload the new artboards you exported in Step 1.