I saw this error (today) on an iPad running iOS 8. I fixed it by executing the reset buttons (hold the power and home / sleep buttons until the Apple logo appears). After that, when I restarted the application, it immediately syncs.
For a simulator, it can be quite simple to exit the simulator and restart. However, I have seen cases where a computer restart is required.
I'm not sure what the cause of the problem is, but hopefully the above help.
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