Recently we became aware of an issue with a bad actor hosting unwelcome content on stores using the same suffix as you, which has now been fully resolved.
Unfortunately, this has caused some platforms such as Facebook to temporarily block things like sharing URL's using that suffix.
We're working with these platforms to resolve the issue, but it could take some time, so a quick solution if you are affected would be to change your URL to a different suffix or consider purchasing a custom domain.