iPad 和 MacBook 都升级到了最新系统，但是调试不出 universal control 。
“Available on MacBook Pro (2016 and later), MacBook (2016 and later), MacBook Air (2018 and later), iMac (2017 and later), iMac (5K Retina 27-inch, Late 2015), iMac Pro, Mac mini (2018 and later), and Mac Pro (2019); and iPad Pro, iPad Air (3rd generation and later), iPad (6th generation and later), and iPad mini (5th generation and later). Both devices must be signed in to iCloud with the same Apple ID using two-factor authentication. To use wirelessly, both devices must have Bluetooth, Wi-Fi, and Handoff turned on and must be within 10 meters (30 feet) of each other. iPad and Mac must not be sharing a cellular and internet connection. To use over USB, you must trust your Mac on the iPad.”