Glad you found a fix. That said, the back up is IMHO kind of a waste. It only backs up the catalog. What about your images, presets? A better approach is to dedicate a drive to all these important files (first set preferences to Store Presets with catalog), then clone that to another drive. Back up the whole shooting match. Plus you can take that drive onto any machine that has a copy of LR, Mac or Windows, double click on your catalog and you’ve got everything you need to keep working. Clone back to the older drive, it backs up only the new data and you’re done.
Maybe someday, LR will have a full and useful backup strategy. Ain’t there today.