There are four criteria (by default) that need to be met for people to be able to report time.
1.) Work item is marked "reportable"
2.) Work item is assigned to the resource
3.) The work item should have started (if it happens in the future, you just need to set a filter)
4.) The state of the work item is active (can change this in the system settings).
Are all 4 of those criteria met? Can you also go to People and make sure that a T&E license is assigned to that individual?