Option 1:
Tighten down all body screws nice and snug and then adjust pivot until it's centered. If the pivot is already good tension, then this won't work because the pivot will be too tight to make it centered.
Option 2.
Take the open knife, serial-number side up and put the blade between drawers or between the bottom of a door and a carpeted floor (have to reverse knife orientation), and make a prying motion DOWN (for drawers) or UP (ZT-logo side up for bottom of door/carpet-floor). Apply medium pressure for a brief moment and then release and repeat until fixed--you do NOT want to break your drawers / door / blade.
Option 3.
Loosen all of the body screws, re-fit them, and then hold the blade center when tightening them.
Usually it's a pivot-tightening issue or a scale-adjustment issue (body screws) and the prying method loosens everything in the scale-fit so that the blade magically moves to the side.
If none of the above works, you can send it in, but I've always been able to center my blades this way.