DueSlotPlanner tasks not showing in Outlook
If Planner tasks used to appear in Outlook and then stopped, the usual reason in 2026 is that Microsoft retired the Planner Outlook iCalendar feed.
DueSlot does not insert events into your default calendar. It uses a separate “Planner (DueSlot)” calendar. After the first sync, open Outlook's calendar list and tick that calendar if it isn't visible — some clients hide new calendars until you do.
Also check: you signed in with a work or school account, the tasks have due dates, and (on Free) you pressed Sync now. Premium Planner plans cannot be read through Microsoft Graph.