It's an easy fix, the only issue with my fix is the light doesn't turn on/off buthe V/S shows and you can adjust it. Here's the fix:

Go to: MSFS\Official\OneStore\asobo-vcockpits-instruments-b747-8\html_ui\Pages\VCockpit\Instruments\Airliners\B747_8\VSpeed

Open B747_8_VSpeed.js with notepad.

You'll find the following:

class B747_8_VSpeed extends Boeing_FCU.VSpeed {
    get templateID() { return "B747_8_VSpeed"; }
    shouldBeVisible() {
        return SimVar.GetSimVarValue("L:AP_VS_ACTIVE", "number") === 1;
    }
}
registerInstrument("b747-8-vspeed-element", B747_8_VSpeed);
//# sourceMappingURL=B747_8_VSpeed.js.map

Copy the following:

class B747_8_VSpeed extends Boeing_FCU.VSpeed {
    get templateID() { return "B747_8_VSpeed"; }
}
registerInstrument("b747-8-vspeed-element", B747_8_VSpeed);
//# sourceMappingURL=B747_8_VSpeed.js.map

Save it and it'll work. Make sure to make a copy of the original in case you screw up and maybe someone else can look into the missing light.