I downloaded the user manual for your system to be familiar with what you're seeing.
My first, probably most obvious question may seem a bit dumb, but please bear with me.
How closely did you follow the setup instructions in the manual - particularly the speaker wiring, connections and assembly?
If meticulous attention is not paid to speaker wire polarity
and connection integrity, it can have the results you describe. That's quite an assembly project, and re-checking the connections is a good idea. Be sure to verify the surround speaker's connections to the WiFi module too.
Note: I am a little dubious about the surround speaker positions shown in their manual. (page 15)
Usually these are mounted on the wall facing into the listening positions, not on the floor as shown.
Frankly, I think the picture is a generic one as it doesn't depict your speakers accurately.
The text however, describes the correct positioning - follow that instead.
You mention "rear" speakers. Your 7.1 system doesn't have "rear" speakers. Instead you have 4 Front speakers -
You should have
- L+R Front plus L+R Top (4 total - arranged in two towers?)
- L+R Surround
- Sub Woofer
Do I have the correct manual - Is what I'm describing what you have?
Rather than go on speculating, I'll wait to see your responses.