Why is my iPhone not backing up into iCloud?
Why is my iPhone 7 Plus not backing up my data into iCloud to free up space?
How do lock my screen when backing up?
iPhone 7 Plus, iOS 13
Question marked as
You lock the screen by pressing the power button. There are probably at least a dozen reasons why it doesn’t back up to iCloud, not just one. So you need to provide additional information, such as what messages you see when you try to back it up. Go to Settings/[your name]/iCloud, tap on Backup and then Back up now. Watch the screen and report any messages you see.