So I selected the sync option on my iMac, had to shut it down as it told me, came back up for a few songs. Then I selected sync option of my iPad, came up with some missing files, and then ST3 on my iMac shut down and would not come back. Deleted the app, and now up and running again. Fortunately I had a full manual back up. Will not be using the sync function again for sure. I was not a Beta tester, so there might be I have done something wrong somewhere. But I will definitely not risk this again.

Same for me, but no way to restart the application, even after reinstalling from Apple Store.
Running Catalina

Crashed Thread: 0 Dispatch queue: com.apple.main-thread

Exception Type: EXC_CRASH (SIGABRT)
Exception Codes: 0x0000000000000000, 0x0000000000000000
Exception Note: EXC_CORPSE_NOTIFY

Application Specific Information:
*** Terminating app due to uncaught exception 'NSInternalInconsistencyException', reason: 'This NSPersistentStoreCoordinator has no persistent stores (unknown). It cannot perform a save operation.'
abort() called
terminating with uncaught exception of type NSException

    giaturr I deleted the app completely from my iMac (in the trash bin), then installed it again.

        giaturr Strange. Hope you had made a full back up before installing. Did you bin the ST3 icon in the trash bin? (Sorry, don't mean to insult your IQ, just trying to help)🤓

            royandreno
            Yes, I kwon know to uninstall app :-)
            And I have a full backup, too.
            But.... I really need the application.......

              Managed to restart the application, after some tricky moves and restarts.
              Cloud Sync will remain disabled; I really was waiting for that features, hoe it will work someday .

              That's really strange. The error message you posted indicates that there is no database existent. A quick search on the developer forums leads to the only hint so far that this error usually disappears after reinstalling the app (and deleting the folder ~Library/Containers/Stage Traxx 3 (Caution, this will delete your data)).

              After that the error usually will not come back. But I have not found a cause for this issue yet. What macOS version are you 2 on?

                Regarding the missing files: This is normal as the database updates first and then the audio files start downloading. During the download you see more on more of the missing marker disappear. When sync is finished there should be no more missing markers.

                I think the message error refers to my post.
                MacOS 10.15.7

                peter
                Tried the procedure.
                The real path was Library/Containers/de.dikant.stagetraxx3
                Downloaded and installed from App Store: the app starts, but no restore is allowed because (it says) it'e free versions.
                Resore Purcheses doesn't work. Sure I'm logged in with my AppleID (in system preferences, Apple Store, etc....)

                Please help,
                Thank you

                    giaturr
                    I buie another license ad Apple Store told me I already had one. Tricky but fair.

                        Anyway, after re-enabling iCloud Sync the app doesn't start, as reported before.
                        I'll save the report and try to revert to non synced version,.... again.

                        Actually it is a good thing that you can reproduce the problem. That way we can find and eliminate the cause a bit easier. Before you reinstall the app, please send me your logfile. If you can not start the the app, the logfile can be found here: ~Library/Containers/de.dikant.stagetraxx3/Data/Library/Caches

                        I saved the report before reinstalling the app. As I told before, I really need it every day (great app, apart from this last upgrade).
                        Can I send the report in a private way?

                          I have a suspicion about a possible cause for the crash but to continue I need to wait for the crash logs that Apple should send me tomorrow.

                            giaturr Please send the log to support@stagetraxx.com. And if you could also send me the crash log. That would help a lot. You should be able to see it in the Console app. Please select Crash Reports and search for Stage Traxx 3 in the list of crashes.