The loopback function is blocking system audio. Fix: Press the "Record" or "Loop" button on the physical V8X Pro unit. If the light is on, your PC audio is being "stolen" by the card. Turn it off. Alternatively, go to Sound Settings > App volume and device preferences > Set your browser to output to "Speakers (V8X Pro)" not "Default."
Power starvation via USB hub. Fix: The V8X Pro requires 5V/500mA minimum. Plug it directly into the motherboard I/O on a desktop, or use a powered USB hub for laptops. v8x pro sound card driver
Many sellers ship counterfeit V8X Pro units. The driver only works for genuine models with the correct USB chipset (usually a modified CM108 or similar). The loopback function is blocking system audio