Every source consulted (Wikipedia's Maple syrup article, the National Museum of the American Indian's own magazine) agrees the practice is ancient and predates European contact by a long span, and Wikipedia states plainly that there are no authenticated accounts of how maple syrup production and consumption began. The earliest fixable date found, 1680, marks European settlers and fur traders already harvesting maple products, a continuation of an established Indigenous practice, not its origin.
What would resolve this An archaeological find (a boiling site, a processing vessel) or a dated Indigenous oral history account placing maple sap processing at a specific century before European contact.
OpenFood history and archaeologyMaple syrup (Wikipedia)