Sometimes we are getting stuck with the Facebook like box positioning issue due to it’s overlap behind other page contents and elements.
We do not require to change z-index property of the parent/container element. Just follow quick fix.
Following is the quick fix to resolve positioning issue:
/* Put it to your style.css */
position: fixed !important;
It will overwrite the Facebook default style with our custom style fix.
Note: If it not works then make sure the parent/container element has css value overflow:visible. It happens when the parent/container element has css value overflow:hidden.