Social media shares not showing up on website & Facebook link thumbnail missing

A few days ago, I found that none of the social share links from Facebook or Twitter, were showing up on my website. I have used the facebook debugging tool, with no success. I have checked the plug-in and deactivated the ones not is use, just in case there is conflict...but still no luck. Does anyone else have this problem? How did you resolve these issues. Thanks so much.