Checked without firewall and still same error. I also checked my other PC and same error there.
Mac Mini and MacBook Pro with OS X 10.11.6 - VirtualBox v5.x running WinXP 64. B4A v6.3 and B4I v2.8
I have only noticed this error recently though I have not used UI Cloud a lot because I have local compile (using latest Xcode v8).
It isn't critical as everything else works but without this feature I can't test layouts on iphone 4.