If you don’t upload symbols when you upload your app to iTunes Connect, Xcode attempts to symbolicate crash logs using dSYM files on your Mac that are indexed by Spotlight. If you include bitcode but not the symbols, you may need to download the dSYM files that the App Store generated when compiling the bitcode before Xcode can symbolicate the crash logs.
In the upper-right corner of the detail area in the Crashes organizer, a Symbolicating spinner appears when you view a crash log. If Xcode is successful, the spinner disappears and the symbols appear in the crash log. If Xcode is unsuccessful, the spinner stops and Xcode will not attempt to symbolicate the same crash log again.
Later, if you add the dSYM files to your Mac and they are indexed by Spotlight, you can try to symbolicate the crash log again.
In the Crashes organizer, view the crash log.
In the detail area, right-click and choose Symbolicate from the pop-up menu.
If the Symbolicate menu item is disabled, the crash log is fully symbolicated or is currently being symbolicated.