The initial 18.7 on Android exhibited some issues on specific devices soon after release, so it was rolled back to 18.6 whilst that was resolved.
As noted above, we have 18.7.2 available, but for the moment we are restricting it to the beta channel so we can have some wider user confirmation that the problems are gone. Once we have that, it will be rolled out to everyone in the store. See
this blog post for more details.
If you're desperate for 18.7, either sign-up for the beta channel as noted above or you can side load it from the download mirrors (link at the top of every forum page). But it shouldn't (hopefully!) be too long before we can release it to the full Play Store audience.
