The learner has now been added into the sampling plan.
There has been some recent changes on Smart Assessor and the learner can only be added once evidence has been uploaded to that course.
You can get around this by doing the following:
1. Go to the learners dashboard
2. Select the course tab you with to add to sampling group
3. Click on "upload work"
This will then allow you to add the learner to the sampling plan.
If you have any problems with this then please let me know.