So this is what worked for me, having had issues from day 1 of getting my Blackshark v2 Pro.
The settings in Synapse 3 had no effect whatsoever on the headset. THX did not work. EQ, etc.
Synapse Beta would not even display the headset so I was at a loss.
I MANAGED TO GET THIS WORKING IN SYNAPSE BETA.
1. UNINSTALL ALL RAZER SOFTWARE
Uninstall it all, make sure there are NO Razer software on the computer.
2. REMOVE DRIVERS FROM DEVICE MANAGER
Go to device manager and see under Audio if the headset is there still. If it is, right click and uninstall it.
3. DELETE THESE FOLDERS FROM YOUR COMPUTER, AND EMPTY YHE RECYCLE BIN.
C:\Program Files\Razer
C:\Program Files (x86)\Razer
C:\Program Files (x86)\Razer Chroma SDK
C:\ProgramData\Razer
C:\Users\<username>\AppData\Local\Razer
C:\Users\<username>\AppData\Roaming\Synapse3
The underlined, italicised locations you may not have. If you do not, that is fine.
4. UNPLUG YOUR HEADSET, AND ANY WIRELESS DONGLES FOR IT FROM THE COMPUTER.
This part is crucial.
5. INSTALL SYNAPSE BETA
6. ONCE IT HAS INSTALLED AND LOADED IT, LET IT INSTALL ANY OTHER DEVICES
7. PLUG IN THE HEADSET, BY WIRELESS DONGLE PREFERRED (IF NOT WIRELESS, USE CABLE)
8. LET IT INSTALL, AND RESTART COMPUTER.
9. IF RAZER SYNAPSE SHOWS IT AS DISCONNECTED AFTER LOADING IT AGAIN, UNPLUG THE DONGLE AND CONNECT IT AGAIN