Login Error: There is an error in logging you into this application. Please try again later

Question

I am getting this error. When I try to sign in with facebook to my app. When I first time authentication it will correctly working. After I unistalled my application and now

Answer 1

The problem for me is really with the hash key, It's not valid.

I had exactly the same problem and it was very hard to diagnose. The reason is that Facebook doesn't check the hash key at first login and it seems that the key is correct, but indeed it's not. Second, the error message is simply an idiocracy. Third is the resolution: try the following link, it helped me.

Better instructions to generate a valid hash key