Make sure no events on that day are set to holiday or "no school."

Here are the steps for the 'trick' that you can follow if you ever run into this again (or you can submit a case and we're happy to help!):

1. On the Rotation Calendar query, click one of the rotation links on the day prior to the day that is missing rotations. In this case, I clicked on one of the rotation links for 11/22/21.
2. In the window that appears, copy the URL, which for 11/22/21 is as follows: https://axiom.veracross.com/gcds/#/detail/calendar-day/44520/802-general
3. Paste that URL into a new browser tab, but increment the record ID (44520) by however many days 'off' this date is from the one that you want to adjust. For example, since 11/22/21 is one day before 11/23/21, I incremented that value to 44521. This gave me the correct URL to access the calendar day record for 11/23/21: https://axiom.veracross.com/gcds/#/detail/calendar-day/44521/802-general
4. Navigate to the 'Rotations' tab and add a rotation record for each applicable rotation day meeting on that date, then click update.

Once I followed those steps to add the US Day C rotation day, the calendar day record then appeared on your Rotation Calendar. Please note that if any other divisions are also meeting on that date, you'll want to go to the record and add those as well.