Backing up my iMac for the first time (system memory approx 15% full) with my new 4TB Seagate Backup Portable Plus. Plugged it in, selected the option to use with TIME MACHINE & checked the box to set up encrypted/password. Got msg that device would need to be reformatted, clicked OK and during that process got an error msg saying there wasn't enough ROOM ??? to complete the task. NOW, seeing msgs that the device is unreadable on my computer; no EFI system partition. Am I just SCREWED or is there a fix?