Hello,
The reason for this problem is that Google has restricted the program's access to external storage in Android 11 and above, please refer to Storage updates in Android 11.
With this update, your access to external access is limited to the Photo & Media folders, and you can't change the external storage yourself.
In addition to this, you need to request storage permissions at runtime, see the following documentation and examples.
var status = Permissions.RequestAsync<Permissions.StorageWrite>();
For Android 11 and above file management, it is more recommended to store files in the internal folder of the program, which can increase security, please refer to Xamarin.Essentials: File System Helpers.
Best Regards,
Alec Liu.
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