If you see such an error when you are trying to link the target iCloud account to your mSpy account please make sure that:
- the iCloud backup is enabled on a target iPhone in Settings -> [your child's name] -> iCloud -> iCloud Backup (the switcher for it should be on/green);
- the manual backup is done in Settings -> [your child's name] -> iCloud -> iCloud Backup -> then tap on "Back Up Now".
In case you have already done that and you still see the error, it means that the backup has not uploaded to the mSpy servers yet. In this case, you need to wait not less than 24 hours since the moment you did a manual backup before linking the target iCloud account again. Unfortunately, this cannot be overridden due to some technical constraints.