@Doudy Hello, Welcome to the 
community. 
Please follow the below troubleshooting steps :
- Reboot the phone to refresh the network signal. (would recommend to remove sim card before rebooting and only inserting after reboot)
- Clear the phone inbox to ensure it is not full.
- Check if there are any phone applications / settings that are filtering SMS.
- Alternatively, please swap the SIM to another phone to verify if the delivery issue is phone-related.
If the issue still persists kindly contact us through our social media channels so that we can help you individually with your issue. Hope this helps. 
Veda | Community Team