Here's how to enable the notifications from Agendrix when you have a Samsung mobile phone.
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The path shown below should be the same in all Samsung devices. If ever you don't find the same steps, you can always refer to this website, which will explain the path according to your OS version.

To do so, you need swipe your screen with your finger from the top in order to display a "cog" at the very top right of the screen
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Once inside the settings, you can click on "Apps", then on the "3-dots" at the very top right of the screen and click on "Special access"
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Click on "Optimize battery usage" and you'll find a dropdown menu at the top where you will need to select the option "All" to show every app on the phone, including those optimized

Then you just scroll down until you see Agendrix and deactivate the optimization. This will let Agendrix run in the background and you will now be able to receive notifications