Need help finding source of CSS in Drupal code
This sounds like a file permission problem on your production server for the library you added to your all/libraries folder. I.e. that some read access to those files in that folder is not granted.

Another reason MIGHT be that your library folder name (within all/libraries) is NOT named share42 (case sensitive, so Share42 would NOT be ok). Variation of that could be that "share42.js" and/or "icons.png" cannot be found in that folder (eg beause it got renamed to something else).