17th Sep 2022 updated
Reminder FLEX has started to support Android 13 Since Ver.9.4
If you use Reminder FLEX on Android 13 and Reminder doesn’t go off
Go to Settings > Apps > Reminder FLEX > Notifications
Turn on “All Reminder FLEX notifications”
Then it should work.
Yet, if you experience any trouble or strange behaviour
Let us know from Contact in the app or here