Firebase 401 unauthorized error FCM

Question

I\'m trying to test out Firebase Cloud messaging APIs as all functionality is not available from console (notably customization of notifications when app is in background).

Answer 1

I faced the same problem.

the problem was that I was using the legacy server key. when I used the new version of the server key the problem solved.

in your firebase console goto settings -> cloud messaging

then use the new server key. it is longer than the old version key.