title: Why is my Ionic Pro build failing in but my local build is fine?
body: <p>I have an Ionic 3 app which I've been developing and I need to move to Ionic Pro and it has not been easy. I use npm-check-updates from time to time but I think that has gotten me in trouble with Ionic. When I first pushed my app to Ionic Pro, the build failed but I googled it and I realized that my Angular version was ahead of Ionic and I had to down-version my app from Angular 4.4.3 to 4.1.3 (thanks to <a href="https://stackoverflow.com/questions/46077427/cannot-find-module-angular-common-http-ionic-3-app">Cannot find module @angular/common/http Ionic 3 app</a>) and rewrite it to work. Fine. But now I am getting another error, and I assume that it is something like this, but I cannot figure it out. I posted something to the Ionic Forum but did not get a response. The error I am getting is below. Any help would be appreciated. I will ask "mother may I" before I update my Ionic app, but I need to know what to roll back to keep building my program. Thanks!</p>
  
  <blockquote>
    <p>[11:08:39] Error: ./~/firebase/utils/promise.js Module not found:
    Error: Can’t resolve ‘promise-polyfill’ in
    ’/usr/src/app/node_modules/firebase/utils’ resolve ‘promise-polyfill’
    in ’/usr/src/app/node_modules/firebase/utils’ Parsed request is a
    module using description file:
    /usr/src/app/node_modules/firebase/package.json (relative path:
    ./utils) Field ‘browser’ doesn’t contain a valid alias configuration
    after using description file:
    /usr/src/app/node_modules/firebase/package.json (relative path:
    ./utils) resolve as module looking for modules in
    /usr/src/app/node_modules using description file:
    /usr/src/app/package.json (relative path: ./node_modules) Field
    ‘browser’ doesn’t contain a valid alias configuration after using
    description file: /usr/src/app/package.json (relative path:
    ./node_modules) using description file: /usr/src/app/package.json
    (relative path: ./node_modules/promise-polyfill) as directory
    /usr/src/app/node_modules/promise-polyfill doesn’t exist no extension
    Field ‘browser’ doesn’t contain a valid alias configuration
    /usr/src/app/node_modules/promise-polyfill doesn’t exist .ts Field
    ‘browser’ doesn’t contain a valid alias configuration
    /usr/src/app/node_modules/promise-polyfill.ts doesn’t exist .js Field
    ‘browser’ doesn’t contain a valid alias configuration
    /usr/src/app/node_modules/promise-polyfill.js doesn’t exist .json
    Field ’browser’ doesn’t contain a valid alias configuration
    /usr/src/app/node_modules/promise-polyfill.json doesn’t exist
    [/usr/src/app/node_modules/promise-polyfill]
    [/usr/src/app/node_modules/promise-polyfill]
    [/usr/src/app/node_modules/promise-polyfill.ts]
    [/usr/src/app/node_modules/promise-polyfill.js]
    [/usr/src/app/node_modules/promise-polyfill.json] @
    ./~/firebase/utils/promise.js 14:76-103 @
    ./~/firebase/app/firebase_app.js @ ./~/firebase/app.js @
    ./src/providers/user.service.ts @ ./src/app/app.module.ts @
    ./src/app/main.ts Error: ./~/firebase/utils/promise.js Module not
    found: Error: Can’t resolve ‘promise-polyfill’ in
    '/usr/src/app/node_modules/firebase/utils’ resolve ‘promise-polyfill’
    in '/usr/src/app/node_modules/firebase/utils’ Parsed request is a
    module using description file:
    /usr/src/app/node_modules/firebase/package.json (relative path:
    ./utils) Field ‘browser’ doesn’t contain a valid alias configuration
    after using description file:
    /usr/src/app/node_modules/firebase/package.json (relative path:
    ./utils) resolve as module looking for modules in
    /usr/src/app/node_modules using description file:
    /usr/src/app/package.json (relative path: ./node_modules) Field
    ‘browser’ doesn’t contain a valid alias configuration after using
    description file: /usr/src/app/package.json (relative path:
    ./node_modules) using description file: /usr/src/app/package.json
    (relative path: ./node_modules/promise-polyfill) as directory
    /usr/src/app/node_modules/promise-polyfill doesn’t exist no extension
    Field ‘browser’ doesn’t contain a valid alias configuration
    /usr/src/app/node_modules/promise-polyfill doesn’t exist .ts Field
    ‘browser’ doesn’t contain a valid alias configuration
    /usr/src/app/node_modules/promise-polyfill.ts doesn’t exist .js Field
    ‘browser’ doesn’t contain a valid alias configuration
    /usr/src/app/node_modules/promise-polyfill.js doesn’t exist .json
    Field ‘browser’ doesn’t contain a valid alias configuration
    /usr/src/app/node_modules/promise-polyfill.json doesn’t exist</p>
  </blockquote>