Thank you for your explanation. I did not click to try the demo, because I will not bother to click on any Like or Share buttons unless I have tried the product. I am not the only one to be fooled by what I see in clear text. The name of Mashshare (unrelated to the plug-in function) made me suspicious and I may have been sensitized by the unrelated web site opened by the plug-in link, which I see has now been changed, since my comment here and on the WordPress Support page - very bad publicity to put the wrong(?) link.

On a subsequent visit to the Mashare site, apart from the prices, I saw at the very bottom:
Note: This addon requires Mashshare installed. So that's why it wont work? There are a few plug-ins that require pre-installation of a specific theme or plug-in, but they give you a warning. What a time-waster. I hope that they get their act together.