iPhone is unable to back up because of iCloud Storage

Hi Louis2448,

The 5 GB may still not be enough iCloud storage to back up your iPhone as indicated by the message.

You can see the potential size of the iCloud backup here:

"If an alert says that there's not enough iCloud storage

1. In iOS or iPadOS, go to Settings > [your name].
2. Tap iCloud. At the top, you can check how much iCloud storage you've used.
3. Tap Manage Account Storage or Manage Storage.
4. Tap Backups, then tap the device you're using. Under Last Backup and Backup Size, you can check Next Backup Size. It may take a few minutes for your device to calculate Next Backup Size. 
5. If your backup needs more space than the amount you have available in iCloud, you can: 

• Delete information that you don't need to reduce the size of your backup
• Upgrade your iCloud+ plan to get more space

If you still need help, contact Apple Support."

You can find these steps along with other information that may be helpful, here: If you can't back up to iCloud - Apple Support

If you have followed the steps correctly and you still have the issue, let us know if you get any specific alerts or error messages when trying, as those may help us determine what might be causing the issue.

We also recommend restarting your device and keeping it updated as those steps assure you have cleared out any minor software issues and are running the most current version.

Restart your iPhone - Apple Support

Update your iPhone or iPad - Apple Support

If you still have questions, reach out to Apple Support directly, as this may require closer guidance: Get Support

Cheers!