Failed to fetch a valid Google OAuth2 access token with firebase-admin - node.js

Question

I currently cannot read or write data using firebase-admin in nodejs.
Without logging turned on it just hangs forever and never returns an error and never completes.
With logging turned on however it gives the following (it continues to retry on a decaying schedule - but with the same result):
p:0: Browser went online.
0: set {"path":"/server/saving-data/fireblog/users","value":{"alanisawesome":{"date_of_birth":"June 23, 1912","full_name":"Alan Turing"},"gracehop":{"date_of_birth":"December 9, 1906","full_name":"Grace Hopper"}},"zg":null}
p:0: Buffering put: /server/saving-data/fireblog/users
p:0: Making a connection attempt
p:0: Failed to get token: Error: Credential implementation provided to initializeApp() via the "credential" property failed to fetch a valid Google OAuth2 access token with the following error: "unable to verify the first certificate".
p:0: data client disconnected
p:0: Trying to reconnect in 0ms
0: onDisconnectEvents
When I catch the (internal to firebase-admin) https request I get the following:
{ Error: unable to verify the first certificate
at TLSSocket.<anonymous> (_tls_wrap.js:1094:38)
at emitNone (events.js:86:13)
at TLSSocket.emit (events.js:188:7)
at TLSSocket._finishInit (_tls_wrap.js:616:8)
at TLSWrap.ssl.onhandshakedone (_tls_wrap.js:446:38) code: 'UNABLE_TO_VERIFY_LEAF_SIGNATURE' }
I have tried generating a new private key from the console but it continues to return the same error. I have also added the require('ssl-root-cas').inject() as suggested elsewhere but it doesn't change the behavior. Also passing the actual json object to the admin.credential.cert function does not change the behavior.
I am currently on node v7.7.4.
Here is the code I have that produces the error:
const admin = require('firebase-admin');
admin.initializeApp({
credential: admin.credential.cert('./serviceAccountKey.json'),
databaseURL: 'https://mtg-decks-bc92d.firebaseio.com'
});
// turn on logging
admin.database.enableLogging(true);
const db = admin.database();
const ref = db.ref('server/saving-data/fireblog');
const usersRef = ref.child('users');
usersRef.set({
alanisawesome: {
date_of_birth: 'June 23, 1912',
full_name: 'Alan Turing'
},
gracehop: {
date_of_birth: 'December 9, 1906',
full_name: 'Grace Hopper'
}
}).then(() => {
console.log('set complete');
});

Answer 1

Several other posts recommend adding the root certificates by calling require('ssl-root-cas').inject();. Can you try that?
Example: Error: unable to verify the first certificate in nodejs

Answer 2

I got this error because my local machines time zone was set manually so the token expiration etc was off.