Smart Logbook doesn’t seem to know that my subscription was renewed.
Sync subscriptions are managed by the App Store (if you purchased on iOS) or by Google Play (on Android). You can use a single subscription to enable sync across multiple devices and platforms, as long as you sign into Smart Logbook with the same account everywhere. For example, an iPad can use a subscription purchased on an Android phone, and an Android phone can use a subscription purchased on an iPad
The one caveat is that subscription renewals must be processed by a device running the same platform where the subscription was originally purchased. For example, if you started a sync subscription on Android, but then switched to iPhone and stopped using Smart Logbook on Android, the app will not be able to detect the next subscription renewal. At that time, it will incorrectly assume your subscription has expired.
To fix this, you need to switch your subscription to the platform where you’re currently using Smart Logbook, via the Purchase screen in the app. Don’t forget to also cancel the original subscription on the other platform. You can cancel an Android subscription via Google Play, and an iOS subscription in the App Store app.