Back in 2002 (and again over the years) I've registered domains through Assurance Hosting. One of my domains was up for renewal so I went to their site only to see a landing page. It appears they've gone out of business and any attempts to contact them have failed.
If you're going through this and think you're about to lose your domain, here's what you can do: Assurance Hosting was an eNom reseller, so you can contact eNom and they'll work to unlock your domain so that you can transfer it elsewhere (during the process, which has been going very quickly for me, you'll need to verify your identity and proof of domain ownership).