Cannot receive messages from self-hosted mosquitto broker


I am using the DISCO-L475VG-IOT01A board. I have successfully developed a program which publishes and subscribes to topics on HiveMQ community broker. I have tested the same with mosquitto community broker and works fine.
I have now hosted my own mosquitto broker on cloud. I publish and subscribe to the broker but I am not receiving any messages from the topic I have subscribed to. nor am I getting any error messages.

What can be the reason for this?
Thank You.