To make sure your battery last as long as possible, Samsung optimizes most apps on your phone, preventing them from running in the background. It does save the battery but also prevents all notifications from these apps to work properly.
Here's how to enable the notifications from Agendrix when you have a Samsung mobile phone.
Step 1 - Open the app settings
To do so, you need to long press Agendrix's icon and then select "App info" when the menu pops up
Step 2 - Optimize battery usage
Once inside the setting, you can click on "Battery" and then "Optimize battery usage"
Step 3 - Show all and deactivate optimization
There will be 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
Deactivate the optimization
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