首先，要确保双方的设备都升级到了 iOS 15.1 版本，如果不确定的话，可以去「设置-通用-关于本机」里看一眼。如果有一方没升级到 iOS 15.1，那么版本低的一方将无法看到共享的屏幕内容。

Though routine support for these models ended years ago, Apple's update is meant to preserve the cryptographic system that keeps older devices securely linked to its services.