An employee cannot find a newly created activity item in the Activity drop-down when entering time.
This can happen if you have turned on Project Assignments for the project the employee is entering time against, or if Manage Access restricts access for that employee. Either restriction limits activities to only those you explicitly assign. To make the activity available, assign it manually through Project Assignments (for the project) or Manage Access (for the employee), or add it to an activity group that is already assigned to the project or employee. This ensures that the activity appears in all the time entry screens for the employee.