My HG has been laid up for some years, so I want to flush the brakes. I don't know how good/bad they are as I've not had it on the road.

I've got a vacuum bleeder kit, but no matter what I do I cant get the fluid to flow. I got a couple drips at first, but nothing since. I can ramp the pressure up, but it just holds it. I've tried pumping the brakes with the nipple released. Even when I take the nipple right out, no fluid comes out the port (haven't tried pumping them like that but).

Is there a technical reason vacuum bleeding doesn't work, or should I be looking for a fault?