I looked up your Amplifier.
It sounds to me like you need to run the "Automatic MCACC".
Your amp has a 5-band EQ for each channel. Some of the channels might be muted by default (Which doesn't make sense, but factory settings are almost always crap, in my experience).
Or if you've already run the Automatic MCACC, there's apparently a way to fix it if you don't like what it did. A way to manually adjust the MCACC and the EQ of each speaker. The Auto MCACC might have tuned down the speakers you cant hear.
I mean, unless the channels you can't hear are just DOA, in which case you need to return the amplifier. But I doubt that's it. That's too nice of an amp for that.
I want an amp that good.