Knocking on the door creates a period of wait with a random length which is only dependent on the driver in terms of maximum (i.e. “wait 1 minute and if no response leave it on the porch”).
So it makes sense that if a driver is excessivelly pressed in terms of time-per-delivery, they won’t do it.
Given the pay for and demands on these drivers, at best expect placing it in the “safe place” they see by skimming your notes and a ring immediatelly followed by leaving without waiting.