unable to get this to work with IOS

I have created an android and iOS versions of my app. in the android part, payouts are working fine but in iOS, they are not.
Basically, I want to payout a driver from PayPal (rider has already paid and money is in my business account) I set up a button 'get payout' and a textview for the driver to input their PayPal email address.
I have firebase-function set up and deployed.
When the driver is ready to receive a payout, they put in their email address (txtPayoutEmail.text) and select the button "Get Payout". This executes the payoutRequest() method which sends the data: uid and email to the function then to PayPal. Paypal should then send a notification email to the driver stating the have a payment.
Whats going on is this:
- once executed, the data is sent to the firebase function: checking logs shows console.info("uid: " + request.body.uid + " email: " + request.body.email) and it shows (in logs) uid: ********** email: *******
- nothing happens on the PayPal end. when I go into developer.paypal.com/notifications, there is no notification sent to the driver's email address.
- from 4 hours to a day, I get a response back from PayPal to firebase function saying missing field: email cannot be null.

Please help!
[index_js.txt](https://github.com/firebase/functions-samples/files/2716520/index_js.txt)
[payoutRequest.txt](https://github.com/firebase/functions-samples/files/2716521/payoutRequest.txt)

Any help would be greatly appreciated!