They have bad label printers that can't handle any address that has extra info in it. Such as Building door codes, or instructions on where to leave the item.
Then when the driver arrives, they can't read the parcel label, because the printer messed it up. So, the tracking says that the parcel is undeliverable.
Then after a couple days, they manually print a new label and only include the most basic address information - which leaves off the information on how to buzz the building to get in the door.
So then the driver shows up, can't get in the building - so they just leave a note telling the customer to drive to teh depot and deal with the problem.
Purolator really needs to figure this issue out, and start delivery parcels properly.