Meteor Cordova: Origin not allowed by Access-Control-Allow-Origin

Question

A mobile build trying to connect to the server throws this error:

XMLHttpRequest cannot load https://www.domain.com/_timesync. Origin null is not allowed by Access-Control-Allow-Origin. Error syncing to server time

How do I fix this CORS problem? I tried putting this code in the server but it still throws the same error:

WebApp.connectHandlers.use((req, res, next) => {
    res.setHeader('Access-Control-Allow-Origin', '*');
    res.setHeader('Access-Control-Allow-Headers', [
        'Accept',
        'Accept-Charset',
        'Accept-Encoding',
        'Accept-Language',
        'Accept-Datetime',
        'Authorization',
        'Cache-Control',
        'Connection',
        'Cookie',
        'Content-Length',
        'Content-MD5',
        'Content-Type',
        'Date',
        'User-Agent',
        'X-Requested-With',
        'Origin'
    ].join(', '));

    return next();
});

I have also tried replacing connectHandlers to rawConnectHandlers and it still throws the the same error.