Maybe because Google doesn't think it's popular enough, I've noticed that too though. The search does work if you search the app id directly though, like one.jwr.interstellar.
If you're trying to login to your fedia account, I've noticed that server doesn't seem to work (which is why it's not in the recommended instances section). It's probably an issue with how they setup the api (you'll notice other mbin instances work with interstellar just fine).