Serial number for 7.1 Surround Sound

It happens to me the same as you, until I saw that our model is not compatible with that application. PS: Sorry for my level of English, I use Google Translate.

Please read 

Synapse doesn't see these headphones

Try synapse 4

I already have synapse 4, 2 devices connected, but the headphones don’t connect, I tried synapse 3 too, they didn’t connect

Do a clean synapse reinstall:

    Uninstall Synapse
    Download & run this tool: https://rzr.to/Tf53xj to remove any razer drivers/leftovers
    Then restart your PC
    Download Synapse 4: https://www.razer.com/synapse-4 and install it as administrator

Also check headphones in other USB port (at least USB 3.0).

It got even worse, now Synapse can’t see my mouse razer naga trinity. 

Device Manager detects it as a keyboard. The mouse does not work at all with Synapse or without

Still I’d search problem in OS.

cmd as administrator → type “sfc /scannow”

You can do clean reinstall, but before installing Synapse 3 or 4 download CCleaner and run a cleanup + do a windows registry cleanup (be sure to backup it before cleanup!).