Unexpected error

What are you doing when you see this unexpected error? Is that what the exact text of the error is?

You would need to contact Facebook about that error and what to do to troubleshoot it.

What did they tell you? Were they able to fix the problem? If not, why not?

You will have to keep trying. That is not an Apple product, so Apple does not provide support for it. You have to get that from Facebook.