I have seen several Forum entries and tens of 1 star reviews about this, so just to mention: The Backup and Sync is not working. It'd be nice if you'd, you now, react to any of the posts.
Another issue is the Web Login for both the forum and the SwiftKey Data page. I don't know if this is a recent development, but Chrome (both mobile and Desktop), and I'm pretty sure Firefox too, are blocking third party cookies. This seems to make it impossible to login with both Google or Microsoft (The Google button is grayed out and other login attempts result in an error that cookies are disabled). Virtually all other Websites I use seem to login with Google just fine, third party cookies enabled or not. For people not very tech experienced it will be impossible to login (maybe that's why I don't see hundreds of posts about the sync issue...).