We may encounter this error message when adding a Custom item to the itinerary of a Reservation. To resolve this error message, we will want to adjust the Date or Time of the reservation. 

If the Item you are scheduling takes place prior to the arrival time of the reservation, we can follow the steps below to adjust the arrival time of the reservation:
  1. From Sales, Click Group Sales
  2. Using the Calendar, Open the reservation in question
  3. In the Arrival Box, click Edit
    User-added image
  4. Adjust the Arrival time to reflect prior to the Custom Item you are looking to schedule in your itinerary
  5. Save
To adjust the date of the reservation, we can reference the following Knowledgebase Solution: How to reschedule a group sales reservation