I have a desk top IMac and recently disconntected it to take it for the summer. I have a date backup attached that I purchased at Best Buy. Evidently when I plugged it back in at my new location, the data backup did not kick back in as I had a notification that my backup has not worked for the past ten days. I would like assistance figuring out how to reconnect this. I am afraid to simply disconnect it. Can someone help me with this? Thanks you!