The Seven Deadly Sins is part of Kodansha Comics, which have been made available on Crunchyroll since their manga platform release in 20131,2. Crunchyroll has all the current chapters of this up to date. As of today, that is chapters 1-167.
You can read it on their website at:
You'll need a Crunchyroll premium account to read all but the most recent simulpub release. You can use this guest pass if you'd like a free 48 hour trial.
As stated on Wikipedia article for The Seven Deadly Sins the availability is based on your locale:
As the series is published in Japan, it is also released simultaneously in English digitally by Crunchyroll in over 170 countries.
You should be able to read it there without an issue unless you're in one of the few unsupported countries, e.g. Japan, China, France, Germany and Italy3.