The SIGABRT is the final step of a crash that's actually occurring because a NSException was thrown (and, as normal, not caught). Almost every NSException will put something in the console log when thrown. You should run your app from Xcode and look in the console log pane, or run the Console app and filter on your app's name, and you should see the exception error message (and possibly a backtrace).
Additionally, in Xcode, if you set a general Obj-C exception breakpoint, your app will stop when the exception is thrown (and before its message has been logged), so you can poke around in your code where the error occurred.
Thanks for the comment but I finally fixed this issue. The URL used in the MacOS-specific code was inadequate (and different from the one that succeeded in iOS)