Ordering in Microsoft's Gantt Visual

This is usually the sort not surviving the query the Service issues, even though Sort by Column is set correctly.

A few things worth checking: is the sort column also bound to an actual field in the visual, not just set at the model level — some visuals only honor sort order for fields actually in a data role.

If the model is Import mode, try a full refresh and republish to rule out a stale cached order that Desktop happened to preserve but the Service's refreshed data doesn't.

And since you're combining a task field and a parent field, check whether the visual only honors the sort on one of the two levels — a lot of hierarchy-aware visuals sort the parent correctly but let the child/task level fall back to whatever order the query returns.