Why does my iphone not want to back up

What is it if it isn’t an error message? The following is copied from that tip. Please follow these instructions and report what happens after each step:

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Connect your device to a Wi-Fi network.

Go to Settings > [your name], and tap iCloud.

Tap iCloud Backup.

Tap Back Up Now. Stay connected to your Wi-Fi network until the process completes.

You can check the progress and confirm the backup completed. Go to Settings > [your name] > iCloud > iCloud Backup. Under Back Up Now, you'll see the date and time of your last backup.

What error message do you get? See here for help: https://support.apple.com/en-us/HT203977