SKError list of in-app purchase errors

Implementing in-app purchases is key to the vast majority of developers.
Unfortunately, these can be tricky to debug without the proper reporting and information.
Here is a list of the most common SKError codes returned by Apple when implementing in-app purchases.

• 0 unknown
  Error code indicating that an unknown or unexpected error occurred.
• 1 clientInvalid
  Error code indicating that the client is not allowed to perform the attempted action.
• 2 paymentCancelled
  Error code indicating that the user canceled a payment request.
• 3 paymentInvalid
  Error code indicating that one of the payment parameters was not recognized by the App Store.
• 4 paymentNotAllowed
  Error code indicating that the user is not allowed to authorize payments.
• 5 storeProductNotAvailable
  Error code indicating that the requested product is not available in the store.
• 6 cloudServicePermissionDenied
  Error code indicating that the user has not allowed access to Cloud service information.
• 7 cloudServiceNetworkConnectionFailed
  Error code indicating that the device could not connect to the network.
• 8 cloudServiceRevoked
  Error code indicating that the user has revoked permission to use this cloud service.
• 9 privacyAcknowledgementRequired
  Error code indicating that the user has not yet acknowledged Apple’s privacy policy for Apple Music.
• 10 unauthorizedRequestData
  Error code indicating that the app is attempting to use a property for which it does not have the required entitlement.
• 11 invalidOfferIdentifier
  Error code indicating that the offer identifier is invalid.
• 12 invalidSignature
  Error code indicating that the signature in a payment discount is not valid.
• 13 missingOfferParams
  Error code indicating that parameters are missing in a payment discount.
• 14 invalidOfferPrice
  Error code indicating that the price you specified in App Store Connect is no longer valid.
• 16 SSErrorDomain
  Cannot connect to iTunes Store (usually when refused to provide AppStore credentials).
• 100 Unknown product identifier
  Usually returned when requestProducts was not called before making a purchase.
• 1001 NSURLErrorTimedOut
  The connection timed out.
• 1003 NSURLErrorCannotFindHost
  The connection failed because the host could not be found.
• 1004 NSURLErrorCannotConnectToHost
  The connection failed because a connection cannot be made to the host.
• 1005 NSURLErrorNetworkConnectionLost
  The connection failed because the network connection was lost.
• 1009 NSURLErrorNotConnectedToInternet
  The connection failed because the device is not connected to the internet.
• 1012 NSURLErrorUserCancelledAuthentication
  The connection failed because the user canceled required authentication.
• 1200 NSURLErrorSecureConnectionFailed
  The secure connection failed for an unknown reason.