Autodesk Platform Services (APS) applications created on or after December 10, 2024, a “Legacy endpoint is deprecated” error is returned
Your 2017 application is "grandfathered." Autodesk is giving existing apps a grace period to migrate, but won't allow new applications to revert to it. There is no sunset date for the grace period to end.
Follow the advice at the top of the documentation you linked, and use