One of my SEO client website had a huge drop of backlink somewhere in March-April-May'2016. I don't find why it had happened.
My guess is that the new version of the website is close to that time
But the URL is still the same. Can it be something with URL security / WWW or Non-WWW.
How can I resolve the problem and most important, how can I get back most of that SEO Juice ?