Done tick button on notification disappear after updating app.

After Ver.15.1, always notification buttons also appear if you are PRO.

If you are PRO & Done ✅ button on notification disappear after updating app, that’s because of update process.
When the app is updating, lock screen notifications from the app are all erased. This is Android behaviour. But the app recovers lockscreen notifications when update is completed.
However, recovered notifications doesn’t have Done ✅ button.
Just like this image. If lockscreen shows “update completed!” & other notification time are the same. In this time, notifications are recovered but buttons.
However, upcoming reminder notifications will have buttons together again.