Cannot fight at Gym
I can pick up items in pokestop and catch pokemon. But when I approach the Gym, I can never use the Gym. It seems that the game will push me out of the range of the Gym. Can any one tell me why?
I've found that occasionally GPS data will be terrible around one particular Gym, causing it to fail to load. I had this problem a lot during launch but it should be a lot better now. You can always try restarting your device as well just in case.