You can't make a backup and "copy" across the license information as easily as that. Perhaps you should consider some disk imaging tool, or bare metal recovery tools instead of relying on MT's internal backup system. But it is not guaranteed to work as MT is not stupid and they know that someone will try that to make illegal copies and will have taken that into consideration when they wrote their license system!
MT's backup is for backup and restore to the same hardware. Not to the same type of hardware between different machines, but the same physical hardware that made the backup in the first place.
For example, before making any major change, you take a backup, you then make the change but mess it up and cannot remember how it was setup before, so you now restore from the previous backup and your job is still safe.
The license data is held separately from the ROS system in a hidden area that is not backed up. Always contact MT support if you need a new replacement key because of hardware failure.
If backing up and restoring to completely different hardware, always consider using export instead. You can see all the data that is backed up, thus making it easier to edit with a text editor and then import that file on the new hardware.