With the below, keep in mind, this is a third party website so official support would be limited.
As there is no styling, this would likely just mean that for whatever reason archive.org couldn’t grab your CSS file(s). Why, I couldn’t say, only archive.org or your hosting provider can. Would check on their next crawl if this would remain but it is not something in our software blocking or preventing this as you can see our website shows up there. Often archive.org just gets an incomplete copy of your site and the next one it’s fine.