Due to the Bluetooth connectivity loss you may get this issue. Ensure that your smartwatch & phone both are within bluetooth range with the alerts turned on in the App. 

Make sure the DND option is turned off in your smartwatch. You can check this by swiping down the home screen

Also ensure the calling option is turned on in your smartwatch. You can check this by swiping down the home screen. 

Make sure your cult.sport smartwatch is properly connected to your smartphone & all the notifications are enabled in your cult.sport watch app.

If the notifications are still not coming, switch off your phone’s Bluetooth and again switch on or restart your smartphone.

You can try reconnecting the smartwatch and your phone or reset your smartwatch

Try to uninstall and reinstall the cult.sport watch app & then begin the binding process with the smartwatch to see if the issue persists.