Alas -- tech support. Let's see if we can get this running for you.
First, do you have any record of what those error messages were? It will help us decide the kind of trouble you were encountering to begin with so we don't repeat the experience.
Next, what model do you have? There are numerous "XL" models. Please advise of the first two characters of your unit's serial number so we know for certain about it's capabilities (mostly, the memory size).
Two questions to next:
First, have you ever made a proper backup of your unit, using either Home, or your PC's usual way of copying files to your PC?
Second, if you look in the following location, do you see a USA/Canada map folder that is the map you purchased?
My Documents\TomTom\HOME\Download\complete\map
Since your unit was running before all of this started, odds are good there is nothing wrong with your hardware, so all we really need to put your unit back to rights is to be sure we can locate a valid map for it. They may well have been correct in asking you to wipe your device clean -- assuming you had access to a map folder - either the backup or the one you purchased. The firmware for your unit and all the rest will be supplied when Home discovers it's missing.