We appreciate that you are trying to read Attack on Titan 51 on Manga Stream, but unfortunately that chapter has expired or been removed from the website.
We routinely remove chapters so there isn't overlap with any publishers that are trying to sell the chapters in official volumes. It's good for the industry if you don't consume entire series in 1 sitting online. Go out and support the growth of manga outside of Japan by purchasing these volumes as they're available.
However, you can always find the latest releases here on Manga Stream, just don't wait too long or you'll miss the chance to read your favorite series in uncompressed high quality. Check out our full list of manga to find something else to read.