Why would they attempt to deliver to Rent Office, I assume is where they attempted to deliver, when they have always delivered to my actual apartment, I was home.

They made a mistake.

UPS sometimes will leave your package at the leasing office when no one answers at the residence

During the holiday season they tend to bring in seasonal drivers who don't know the usual routine and are probably behind schedule

If you are not present at apartment then only they will deliver at leasing office to ensure that its delivered to you properly