Uploading the *.ipa file with the Application Loader completes and uploads the file to the App Store. After it is uploaded the automated code checking removes it from the queue and provides the following message (actual app name replaced by <>):
• Non-public API usage:
• The app references non-public selectors in <>.iOS: addTemporaryAttribute:value:forCharacterRange:, addTemporaryAttributes:forCharacterRange:, behaviorWithType:, defaultBaselineOffsetForFont:, defaultLineHeightForFont:, finished, greekingThreshold, horizontalCornerRadius, initWithSource:convolutionState:weights:, initWithType:, postSession:didAddPlayer:, postSession:didReceiveData:fromPlayer:, postSession:didReceiveMessage:withData:fromPlayer:, postSession:didRemovePlayer:, postSession:player:didChangeConnectionState:, postSession:player:didSaveData:, preferredMetalContext, removeData:, removeTemporaryAttribute:forCharacterRange:, setGreekingThreshold:, setHorizontalCornerRadius:, setIsPrimary:, setShouldAntiAlias:, setUUID:, setVerticalCornerRadius:, shouldAntiAlias, temporaryAttribute:atCharacterIndex:effectiveRange:, temporaryAttribute:atCharacterIndex:longestEffectiveRange:inRange:, temporaryAttributesAtCharacterIndex:effectiveRange:, temporaryAttributesAtCharacterIndex:longestEffectiveRange:inRange:, textContainerChangedTextView:, toolTip, usesBackgroundSession, verticalCornerRadius
My app was successfully submitted for TestFlight on 4/1/2019. The same code, with the version and build number changed, now fails with the above message. I am using VS 2019 with current versions of Xamarin. Forms, Xamarin.Android, and Xamarin.iOS.