Ahhh! Glad you found that issue.
For social sharing, that is something you'll likely have to wait for putting your site on a real domain. Most of the social sharing features will try to 'scan' the page being shared. The scan is two-fold: 1) to see information about the page for the post that will be created in a users feed and 2) to ensure the page isn't malicious, spam, porn, etc.
Until your site is live and accessible, you will likely run into some issues with sharing, though generally the buttons should generally show so that you can see what they will look like.
I hope that helps explain, but should you need anything else, just let me know!
Thanks,
Alex