Unable to restore backup from iCloud in iPhone 12 pro max

Yes. You can erase your new phone and run the setup again. Apple cloud servers are seeing outages and general slowdowns around product launches this week so I would check them before trying a restore.

• https://www.apple.com/support/systemstatus/

You need these to be working for a restore: App Store, Apple ID, iCloud Account & Sign In, iCloud Backup, iOS Device Activation.

Others may be needed depending on your settings and expectations. Your process is solid and there’s not much you can do - whatever is in iCloud is all you can get so hopefully it’s just slow internet and you don’t have to get Apple Engineering involved to look at your backup logs and perhaps fix or deliver news on what can be restored at this point.