WhatsApp not backing up despite available space on iPhone 14 Pro

Make sure you’re using latest version of WhatsApp. Their developers have had a lot of issues lately. They released something like 14 or 15 updates in last month. Everyone was for bug fixes and optimization. You may also want to contact their support team. They may be aware of the issue.

‘What troubleshooting steps have you done so far?

Why is you iPhone on low power mode and in airplane mode?

You also need 118GB probably x2 of iCloud storage. What plan have you purchased?

You could clean up Whatsapp in the app itself starting with all those kitten videos.

118GB - wow!