PHONE_REGISTRATION_ERROR / UNIMPLEMENTED GCM error on a device using javascript

We are using devices which has Linux OS, javascript enabled (using node.js). We are using google FCM to receive notifications. We are using a javascript library (added register() here) to get the fcm token by passing sender ID. It was all working fine. But from past few days we are getting PHONE_REGISTRATION_ERROR and UNIMPLEMENTED error / UNIMPLEMENTED error when we are trying to get the FCM token.

Below is the code snippet.

(async () => {                                                                                           
  try {                                                                                                                        
    const credentials = await register(senderID);
    const token = credentials.fcm.token;                                                                                                                                                               
    const persistentIds = [];
    await listen({ ...credentials, persistentIds }, onNotification);                                   
  } catch (e) {                                                                                                                                
    console.log("Error::" + e);                                                                                                                
  }                                                                                                                                            
})();

Below is the code for register function

const uuidv4 = require('uuid/v4');
const { register: registerGCM } = require('../gcm');
const registerFCM = require('../fcm');

module.exports = register;

async function register(senderId) {
  // Should be unique by app - One GCM registration/token by app/appId
  const appId = `wp:receiver.push.com#${uuidv4()}`;
  const subscription = await registerGCM(appId);
  const result = await registerFCM({
    token : subscription.token,
    senderId,
    appId,
  });
  // Need to be saved by the client
  return Object.assign({}, result, { gcm : subscription });
}

From past few days we are getting PHONE_REGISTRATION_ERROR and UNIMPLEMENTED error like below.

Register request has failed with Error=PHONE_REGISTRATION_ERROR
Retry... 1
Error::StatusCodeError: 501 - "{n  "error": {n    "code": 501,n    "message": "Operation is not implemented, or supported, or enabled.",n    "status": "UNIMPLEMENTED"n  }n}n"

Or some times UNIMPLEMENTED error alone and unable to get the token. I tried to restart the devices multiple times but of no use.

I went through lot of questions online. All are showing issues with Android apps where the solution is like to clear cache, remove app and reinstall app. But I couldn’t find a solution for this javascript based program. Can someone please let me know if there is anyway to solve this issue.