Hi Gianni,
I have demoed v9.0, but I never tried a backup. I have not used or tried 9.1. But, I am beta testing v9.2, and I was just able to do a backup to an .enc file and then restore from it with no issues. Not sure what that means.
But, for the time being, I would recommend separating your Imported Items from the .enc file. This would solve you upload/download problem.
It would appear it is for the same reason. Whether it is the backup file or a 24 hour activation key, AC doesn't want AC being installed on a new machine either in your office or another office without their being aware of it.
