I had issues with these a while ago, the reservoir bladder had a hole in, so was leaking fluid. Replaced that, at last and tried to bleed and not getting anywhere.
In short, I can't force the fluid up from the caliper to the lever reservoir. I can't use the lever to pump fluid from the reservoir either.
When I squeeze the lever fluid flows, when I release the lever fluid flows back. It's as if there was some sort of fault with the lever, but I've no idea what.
I'm bleeding as per the instructions that are on Pinkbike, so it's not as if I'm doing it 'wrong'.