A visit plan can fail to populate any visits in the user's calendar for several reasons. One possible reason is that the filters and spelling are incorrect or inconsistent, which can prevent the visit plan from finding the right customers or accounts. Another possible reason is that the customers are not within the driving range of the user, which can make the visit plan unfeasible or inefficient. A third possible reason is that there are too many customers assigned to the user, which can exceed the capacity or availability of the user. These reasons are explained in the Troubleshoot Visit Plans document.