If you are having trouble publishing a one-time schedule, it may be due to a known bug. Occasionally, we have seen that creating a one time schedule on a template will not create an event instance after saving and publishing, even if there is no conflict with open hours, holidays, or previously deleted instances for the same event.
The known work-around is to set the schedule as a "Weekly" occurrence for a longer span of time (e.g. 6 days) and only select the day of the week the event occurs. For example, for a one-time event on Valentines day, set the schedule to 2/10/20 - 2/16/20, and set the Occurrence to Weekly but only select Friday (creating one event on Friday Feb 14th).