With Android Nougat, the Theme Store is no more available.
SwiftKey Beta 22.214.171.124
On my Mobile with Lollipop, it isn't an issue.
I have de-/ install the Application several times, the Beta and the official released version. I have delete the cache and Data of the app. I have give the app all permissions, which I can, I have disabled and enabled the account.... No way to reached the store to select add Themes. There are only the few themes available and visible which are coming during install.
The app will not download any previews or something more....
If I create an backup via Titan on my mobile and restore this one on my Tablet, I can select the restored Themes on the button (replaced the keyboard keys) but the store by himself doesn't work.
The apk is registered and the Accound ID is still available in the settings. The account is still aktiv.
Lollipop works fine with the official and beta version
In Nougat it looks like, that the Theme Store isn't reached (or some internal paths are no more valid)