Make sure that you have created a workflow, and enabled it by creating a Trigger (content > publish > before). Once you have it enabled, the notification option should appear.
If you do have it enabled, it could be that the user trying to create the notification on collaboration is not set to be an approver in the workflow.
My Workflow is enabled, and is working properly. The content to be approved appears well on the 'collaboration' folder of each user that is an approver.
You must be logged in to post messages in this topic!