If you can't back up to iCloud
2023年11月8日 — If a message says that your last backup couldn't be completed · In iOS or iPadOS, go to Settings > Wi-Fi. · Go to Settings > General, then tap ...
If you can't back up to iCloud
Go to Settings > General, then tap Software Update. Download and install any available updates for your device. Try to back up on another Wi-Fi network. Check to make sure that you have enough iCloud storage for the backup.
Solved
2023年10月25日 — Why can't you backup your iPhone? One of the most common reasons for a failed iCloud backup is a lack of sufficient iCloud storage. Your iPhone ...
iPhone Backup Failed for Not Enough Space in iCloud
Go to Settings > General, then tap Software Update. Download and install any available updates for your device. Try to back up on another Wi-Fi network. Check to make sure that you have enough iCloud storage for the backup.