At this point, I don't even know if I'm just spamming this thread (if so, my apologies), but I had to get in contact with Norton Support on Twitter, as I still couldn't get access to the All The Anime website with the Chrome extension. I had to go on Norton's support website to submit information, and thankfully, as a result, the All The Anime website is officially marked as "safe" again.
I've heard that Norton Chrome extension causing no end of trouble now they're forcing people into installing it to get rid of the at risk warnings. If you're on Windows 10 I'd advise getting rid of it completely - the built in security stuff is actually pretty good these days and third party AV often interferes with the normal operation of the OS.