Recently, some of our service providers have changed how share counts are stored. Rather than showing the same count for both http and https sites, counts are different based on the different protocol. Unfortunately, we have no control over how these services handle counting shares, so share counts are going to be different for http and https.
This is also the case if you set up https on your site and then set a 301 redirect to the https version. Facebook will crawl the http page, see the redirect, and then update their internal share counter system to show the new URL and reset the share counts.
Because our tools use the tag (shown below) as the definitive URL to use to share and get share counts for, you can set this tag to the URL that has the number of share counts you want to show. If your http link has more shares, the tag on your page will look like this:
<link rel=“canonical” href=“http://www.example.com/” />
However, if you’ve set up a 301 redirect from your http site to your https site, Facebook share counts may be reset.
Hopefully this blog post clears up any issues you may be having with share counters and allows you to restore the lost counts on your page. Learn more about using canonical URLs here.