Generally speaking, when you know something like an update is on the Play Store, but it's not showing up for you in the Play Store on your phone, close the Play Store app, clear out its cache, and restart the phone.
I found also if you search for the app in the Play Store rather than looking for the update on your list of installed apps, the update will appear.
6 months later, I'm disappointed no one told you to check Lineage. They support a lot of Motorolas