Q: iCloud backup not working

Hi T2DTST,

Welcome to the Apple Support Communities!

i understand that you are having an issue backing up your iPhone using iCloud and are receiving an error concerning iCloud storage space. To troubleshoot this situation, please read over and work through the steps located in the attached article. 

Get help backing up your device in iCloud - Apple Support

I can't make a backup because there's not enough iCloud storage

A message might say you're running out of storage, but your device shows there's plenty. There's a difference between how much storage you have on your iOS device and how much you have in iCloud.

If you need more iCloud storage to back up, a message will say that you can't back up because there's not enough iCloud storage available.

Here are some tips if you're low on iCloud storage:

• Upgrade your iCloud storage plan.
• Make a smaller backup. You can back up fewer apps or delete unwanted photos and videos.
• Delete older backups that you don't need.

Best regards