Sometimes, there are a few stumbling blocks. Do some reading about Mission Planner setup. There is a way to turn off the pre-arm checks. But in my opinion, they are there for a reason. I live under a giant tree canopy, and sometimes turn off the GPS pre-arm check. I also had a flashing yellow on my Y6, the other day. Brought it inside, connected to Mission Planner, and got a message that the compass was out of wack. THEN, I remembered I had sat it over night, next to my power backup system, for my flat screen TV. I think that messed up the compass. I re-calibrated, and everything was fine. If you do not have the 3DR radio setup, it is almost impossible to get a good compass calibration, with a wire connected to the computer. Too many turns, flips, rolls, etc. etc. to do.