React Native packager isn't including a 3rd party library in the bundle - reactjs

Question

What's the best way to debug the react-native packager not including a dependency in the output bundle? What I have:
Module is included in package.json and appears in my node_modules
I'm using typescript, and the compiled js file has the require('countdown') line.
If I inspect the output bundle, or log the var countdown = require('countdown'), I can see that the source for countdown.js isn't included in the bundle.
If I use webpack to create a web bundle, it works as expected.
Here's the compiled js code which is having issues:
"use strict";
var __extends = (this && this.__extends) || (function () {
var extendStatics = Object.setPrototypeOf ||
({ __proto__: [] } instanceof Array && function (d, b) { d.__proto__ = b; }) ||
function (d, b) { for (var p in b) if (b.hasOwnProperty(p)) d[p] = b[p]; };
return function (d, b) {
extendStatics(d, b);
function __() { this.constructor = d; }
d.prototype = b === null ? Object.create(b) : (__.prototype = b.prototype, new __());
};
})();
Object.defineProperty(exports, "__esModule", { value: true });
var RX = require("reactxp");
var countdown = require("countdown");
var styles = {
outerContainer: RX.Styles.createViewStyle({
flexDirection: "row"
}),
innerContainer: RX.Styles.createViewStyle({
flexDirection: "column",
alignItems: "center",
paddingHorizontal: 5
})
};
var CountdownTimer = (function (_super) {
__extends(CountdownTimer, _super);
function CountdownTimer() {
var _this = _super.call(this) || this;
_this._setStateToNow = function () {
_this.setState({ currentDate: new Date(Date.now()) });
};
_this.state = { currentDate: new Date() };
return _this;
}
CountdownTimer.prototype.componentDidMount = function () {
this.timerId = setInterval(this._setStateToNow, 1000);
};
CountdownTimer.prototype.componentWillUnmount = function () {
clearInterval(this.timerId);
};
CountdownTimer.prototype.render = function () {
// THIS LINE FAILS SINCE 'countdown' is {}
var diff = countdown(this.state.currentDate, this.props.untilDate, CountdownTimer.DIFF_ARGS);
....
};
CountdownTimer.DIFF_ARGS = countdown.DAYS |
countdown.HOURS |
countdown.MINUTES |
countdown.SECONDS;
return CountdownTimer;
}(RX.Component));
exports.CountdownTimer = CountdownTimer;
The error I'm getting is Object is not a function, and logging the var countdown shows it is {}, and inspecting the index.android.bundle shows that the source code for countdown.js isn't included.
I am running the packager with node ./node_modules/react-native/local-cli/cli.js start