I just updated to Xcode 8 and iOS 10.
After creating a build, I'm running into an error which I think is contributing to some data not getting fetched.
I don't know where to go from here, but it appears to be related to http calls somehow. Either way, I don't like the looks of these errors and need to get to the bottom of things.
In the log I get:
 nw_connection_write_close 9 Connection is not ready, sending error callback
 __tcp_connection_write_eof_block_invoke Write close callback received error:  Socket is not connected
We got the same error. The problem was that we used background without having the key in the info.plist file (see image below).
After we fixed this, the error message disappeared. Instead we got a lot of log messages, which you can turn off (see Hide strange unwanted Xcode 8 logs).
I hope this helps.