This is a known issue for the AppBuilder WIndows client and I am sorry to hear that you have encountered it on your side.
The problem is related to that iOS 10 has deprecated a protocol, which AppBuilder Windows Client is using to communicate with iOS devices. More information about it is available in this forum post
The fix is already on its way and should be released by the end of the next week.
I'd suggest keeping an eye on the above forum post for any further updates. We are going to update it with any new information relating the issue.
Telerik by Progress