The most likely case is that the event is not marked as "Busy". Certain events do block time, like appointments, while others don't, like if you had an event you just needed to know about but weren't attending. This is what the "Busy" toggle is for in the event's settings. Click on the event and make sure "Busy" is turned on to ensure FlowSavvy knows to schedule around that event.

If the event is marked as "Busy", the task might be fixed at that specific time, like if you dragged it to that time and locked it there. To make sure FlowSavvy auto-schedules this task, click on the task and make sure "Auto Schedule" is turned on.

If neither of the above are the case, the event is likely a new event that has been synced in from an external calendar like Google, iCloud, or Outlook, and the schedule has not been recalculated yet. The schedule is not automatically recalculated when changes are made in external calendars, because this would result in a lot of unintended/unexpected moving. Click "Recalculate" to make FlowSavvy recalculate your schedule, which will move those auto-scheduled tasks.