Simple Social Button uses Facebook’s like button plugin.
Facebook’s like plugin uses tracking methods in its like plugin which is used to generate the like button.
You can find these settings in your browser’s privacy settings.
What do the above lines mean?
This issue is client-based, if one of your users doesn’t want to share the data and blocks the trackers to run, then like button scripts most likely will not run which cause it not to show.
If one of the users doesn’t want to share their data and chooses to block the trackers, then the like-button scripts most likely will not run which causes the like-button not to show.
Ref: https://developers.facebook.com/support/bugs/854001531875629/