Cloudflare and archive.is apparently don't agree on how to implement DNS, so if you're using 1.1.1.1 (like myself) you'll get an error. This is the explanation I had seen elsewhere and I was like "Yep, that applies to me." (I assume it's happening with all variations of the archive site including archive.ph)
I found this^1 by searching around HackerNews, seems like a relatively decent overview of what is happening. Kinda paints the archive team in a not-so-great light, in respect to privacy considerations, in my opinion.
8.8.8.8 is Google's DNS, which is not very privacy respecting of which sites you access. 1.1.1.1 is Cloudflare's and it is a lot more privacy-respecting while still being imperfect. However their track record in the privacy/security community is currently quite good, so it's up to you if those imperfections are a problem or not.