I am facing this strange issue in case when user taps on FBConnect button the facebook pop up does appear shows a message "Connect to Facebook" but after few seconds the pop-up goes blank. Please refer the image for more details. I have tried to log the error and enabled break-points over the error delegate methods but control never reaches to those methods. I have never faced this issue before and everything seems to be working fine but now out of the blue this issue came. Initially I thought that the API key got expired, hence change the same but it didn't fix the problem.
I have fixed this issue by updating my Facebook SDK to version 3.0. Previous version of this SDK are obsolete now.