I found that I just keep adding water, (it holds a surprising amount!) and it gets to around 50% in just chamber A. However, I think that 50% is good, but it could be lower than that and be fine.
You can't see any veins? What candler are you using? I also usually find it easiest to candle with air cell side down. I'm sorry.
What's the humidity been? How many thermometers do you have? Maybe the thermometer is off, maybe the incubator is off... I don't know.
Post plenty of pictures, please! Do you have a separate calibrated thermometer and hygrometer? I'm literally sitting in front of chicks that hatched a few days ago from this incubator, lol!