This add-on seems to rely on an internet service to function, meaning when the server goes down you lose access to your saved tabs. I'm not sure if it even stores a local copy of saved tabs, because when the server went down (the entire website was suspended by the server host), all my saved tabs vanished from the add-on. As soon as the service was restored, I moved all my saved tabs to Tab Stash, which is an add-on that does essentially everything this add-on does, but without trying to get you to pay for a subscription, and without relying on a sketchy internet service that could shut down at any time and without warning.