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Have you simply tried re-pinning it to the taskbar? This may resolve the issue.
Otherwise, try this: Right click an empty area on the taskbar and navigate to Properties>>Start Menu (tab) and ensure the option "Store and Display Recently Opened Items in the Start Menu and on the Taskbar" is checked. Apply settings.
It may take some time for them to start displaying again, as Windows will need to repopulate the recent items/places list.
Hope this helps