You are not the first to report having trouble with the newer iPhones. You need to report this to Yuneec CS. We are not affiliated with Yuneec and are just Yuneec users like yourself. If it is not reported to CS nothing will get updated to keep the app compatible with the newer phones and OS’s.
In the meantime try putting the iPhone in airplane mode, then enable WiFi and try to connect to the Breeze when you see the green flashing LED in the arm. When connected it should become solid green with an occasional green flash. Once you get that, open Breeze Cam and enter Tasks so the telemetry icons appear across the top. If they are grayed out and a WiFi connection was established then the Breeze is not fully connected. If that is the case, then hopefully you still have the old phone. It will still be usable even without a SIM card installed.