I’m Disappointed

Fast Track Ultra 8 Only the front and back inputs 1,2 works

Hi!i own the Fast track Ultra 8 and i want to do a live recording with 5 microphones...the problem is that only the front and back inputs 1,2 works.
I have checked the driver's software and channels 3-8 are grayed and i can't do a thing to activate them.i'd appreciate if you tell me how to activate all the other channels.Thank you
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