Push notifications

Hello, before I asked the question, I searched the kodular community, my question is about push notifications when I used firebase cloud Messinging and used fire messaging extension , it worked at first, but then I got an error message “firebaseapp name default already exists” And when I used onesignal, it did not appear to me that the user subscribed, and I used onesignalfix extension and it did not work. I want a solution or any add-on that works or helps , Thank you.

Ys, as mentioned here [Discontinued] OneSignal Fix Extension - #125 by Sumit1334
And a solution has also been mentioned there. .



Is there a free FCM solution for firebase? Notifications work yes, but I get the message “firebaseapp name default already exists app”