Backup failed

I purchased a new iPhone 12 mini yesterday, and I traded my iPhone XS in at the same time.

I backed up my iPhone XS, then wiped it as per normal procedure.

After setting up my iPhone 12 mini in the Apple Store, it updated the software then asked me to restore from a backup. I selected my latest backup and it immediately crashed the app and goes back to my home screen. Every time I turn my phone on now, it starts with the post-update "Hello" screen and says "Backup failed". I am given the option of trying again (fails) or select different backup. I have tried every backup that's stored in iCloud, they all fail and bring me back to the homescreen.

While I would really love to get the backup working, if we can't do that I at least want to get out of this infinite loop where I'm always brought back to the update screen when I turn the phone on.

I appreciate any help, quite a frustrating issue to say the least.