Tek Light Ballast problem

[Zoaelite]

Just purchased an 8 bulb 39W tek 5 fixture used for my zoa tank, the lights were all running at the buyers house but when I got home the rear two lights won't start up. Before I order a new ballast I wan't to make sure it's not an easy fix.

The reason I'm confused is because of reading this:
Check to ensure all T5 bulbs are properly locked into place. This is accomplished by turning the lamps 1/4 turn in either direction and can be tricky.
Ensure that all T5 bulbs are installed. With T5 fixtures all bulbs for each ballast must be installed to work correctly. (For example a Tek Light with 8 bulbs has two ballasts; one controls the outer four bulbs while the inner four are controlled by the other ballast).
Are any of the bulbs lighting or just half of them?
Are the lights flickering at all?
Switch bulbs into different positions in the fixture to find out if there may be a defective bulb.
If none of the above works proceed to complete the RMA form.

Why would only two bulbs stop working? Is it possible that a wire got loose during the transport?