Mute button?
How do you know that the volume is maximum - some control, software slider...what?
What are the existing audio source(s), speaker connections (wired, Bluetooth...) and speakers? Make and models?
All the wires plugged in? Power to all devices? Any interim switches - some A B switch to change signal source or signal destination?
What configuration options are available: both software and connectivity: RCA, 3.5mm, etc..
Do other speakers work?
Do other sound sources work?
More information is needed.