Hi Ankur Vig !
It is not possible to use “remote push notifications” without building your own MakeItNative or Native app through https://docs.mendix.com/refguide/native-builder#1-introduction. Since this would allow everyone to send push notifications to other people’s make it native app which downloaded from App store or Play store. So you have to create your own app
Hope this information is clear enough.
Thank you Mehemet,
With your help I solved the problem. I was running the project without adding the google-services.json (Properly)
When your devices is showing up in the list of devices of the module, it does not proof that the device is registered with firebase.
When your app device is not registered with firebase at all. You will get this SENDER_ID_MISMATCH error.