We have the Triton Ceiling Fan by Harbor Breeze. We have installed it on a vaulted ceiling. Problem is: it won't hang straight. The down rod rubs against the canopy cover.
How can we straighten this out?

What is the pitch of the ceiling? A 12/12 pitch or steeper won't always accept a fan, you can build a small 12/12 box and attach to the ceiling to give you a flat anchor point.

Most fans clearly state the maximum ceiling slope they can handle, some show a picture on the box. We still don't know you slope but you should determine this and we can help if you're not sure how to measure.

You need a vaulted ceiling kit, available from most ceiling fan retailers and manufacturers.