If your student sees the message that there are no assignments available for them to complete, follow these steps:
Check to ensure you have an assignment live in your Legends of Learning account. If so, note what group(s) the assignment is assigned to and proceed to Step 2.
Ask the student what username they are using to sign on.
Go to your Students page and look up the exact username that the student provided you.
Tag that username to the group that your assignment is assigned to.
Alternatively, you could ask the student to sign in with their username that is already tagged to the appropriate group.