Step by Step Troubleshoot V4A
Make sure your device is rooted and install latest SuperSU or SuperUser.
Make sure you install correct apk for your android version.
1. Complete Uninstall V4A (driver + app) and reboot.
2. Install V4A as USER app, begin with battery saving mode.
3. Use Normal mode, go to Sound settings>Music effects> and choose V4A(either fx or xhifi).
4. If not working, switch to Compatible mode, go to sound settings>music effects> and select something else besides V4A.
5. If not working, return to Normal mode, change sound settings, enable Force-Enable.
6. If not working, repeat step 1 to step 5 but as SYSTEM app.
7. If nothing works. Disable or remove the default sound effect under MusicFX, then return to Normal Mode.
8. If no help, submit a bug report.