iOS ApplePay PKPaymentAuthorizationViewController not appearing in Xcode11/iOS 13 - ios

Question

Our application has had ApplePay implemented for a number of years. Just recently I hit the button to trigger it to only find out the pay sheet from PKPaymentAuthorizationViewController doesn't appear. It won't slide up in a sandbox (i.e. simulator or device connected to Xcode) environment, but putting a breakpoint shows that it is being created successfully. It's been awhile since I've tested this, but I am suspecting something change with Xcode11 or iOS 13.
My code is pretty standard Apple Pay, but posted below.
let item = PKPaymentSummaryItem()
item.label = "Our Label"
let price = NSDecimalNumber(mantissa: UInt64(totalPrice), exponent: -2, isNegative: false)
item.amount = price
items.append(item)
request.paymentSummaryItems = items
if let applePayController = PKPaymentAuthorizationViewController(paymentRequest: request) {
applePayController.delegate = self
present(applePayController, animated: true)
}

Answer 1

This will happen if the merchantID used by your PKPaymentRequest is not listed in mobile.entitlements. Or if the MerchantID is not enabled by your app's provisioning profile.
View Controller
PKPaymentRequest *request = [[PKPaymentRequest alloc] init];
request.merchantIdentifier = "com.your.app.merchandId"
mobile.entitlements
<dict>
<key>com.apple.developer.in-app-payments</key>
<array>
<string>com.your.app.merchandId</string>
</array>
</dict>

Answer 2

I was facing the same issue, where Apple Pay suddenly stopped working in our app. We've also been supporting this for at least halve a year now.
Using the latest Xcode (Xcode 11.2, Beta 2 (11B44)), it seems to work again.
I'm guessing it was a Xcode bug then. Even though it's not listed in Xcode's release notes for Xcode 11.1 or Xcode 11.2 beta 2.

Answer 3

I have pasted your snippet into my app, which uses ApplePay and I have run it on a test device which is sandboxed and has ApplePay enabled and the ApplePay button didn't work.
What I found it quite surprising.
When you look at the docs for PKPaymentSummaryItem it has only two initialisers:
init(label: String, amount: NSDecimalNumber)
init(label: String, amount: NSDecimalNumber, type:PKPaymentSummaryItemType)
And neither has default values, but you are initialising one with an empty initialiser. Surprisingly there are no errors or warnings and it even comes up in code completion.
So I changed the initialiser:
let item = PKPaymentSummaryItem(label: "Our Label",
amount: NSDecimalNumber(mantissa: UInt64(totalPrice),
exponent: -2,
isNegative: false))
request.paymentSummaryItems = [items]
if let applePayController = PKPaymentAuthorizationViewController(paymentRequest: request) {
applePayController.delegate = self
present(applePayController, animated: true)
}
And it works (on device only - not simulator)!
That made my wonder so I just changed your item from let to var and it works as well. I would still go with the documented initialiser.