Yeah I experienced something similar yesterday when I was doing some testing. From far away, I could see the SSID and the signal looked good, but when I tried to connect to it with my phone I got the same error message as you. Then when I got closer to the node, like across the street, I was able to connect and had a good speeds ~10mbps. Then I started walking away towards oscar grant. I remained connected and still was getting pretty good speeds - I could watch youtube videos and was getting ~5mbps down. But then when I turned my phone's wifi off and then back on and attempted to connect again from the spot I was in, it refused to connect.
So I think there's some strange issue with the actual process of connecting to the node even in places where there's pretty good signal. I'm gonna try consulting the internet and maybe the ubiquiti forums to see if there's some config or something that I missed.
If anyone else has ideas or experience here, I'm open to any/all ideas.