Steps I took that resulted in the problem:
Installed and tried to run
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What I expected should have happened instead:
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My version of Fritzing and my operating system:
MacOS 10.15.4
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Please also attach any files that help explaining this problem
Welcome aboard! While I don’t know Macs at all, in the github issues section there is a report from someone running Fritzing 0.9.4 on Mac OS 10.15. I’d probably suggest opening an issue on github here:
if no one has a suggestion here. You also may want to try 0.9.3b (assuming you are currently on 0.9.4 which is the latest release) to see if that works.
Peter
I can’t find that version to download.
On the downloads page (assuming you are using the Fritzing site to download of course) below the current version there are previous versions:
Peter
The older version runs, that is odd…
I see the latest version has a couple of MacOS names (no version numbers), is 10.5 older perhaps? The new release is using an entirely new tool chain (as the one used for 0.9.3b in 2016 no longer exists.) It is possible they didn’t (or couldn’t) support older Mac versions, but I don’t really know. Probably your best bet would be to open an issue on github and ask if they do support MacOs 10.5 on 0.9.4 or may add it in a future release. As I said I am not familiar with MacOS, so I don’t know what is involved or thought to be supported now.
Peter
Sorry, I am on the latest MacOS release… 10.15.4
Then as far as I know 0.9.4 should work as well as 0.9.3b. I’d suggest reporting this as an issue on github so it gets tracked and hopefully addressed. The folks that make the releases do sometimes read the forums, but they should get notified by email of an issue opened on github. I expect they would appreciate any error message that comes up when 0.9.4 doesn’t run as well. Sorry I can’t be more help 
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Peter
Well, I’m using Fritzing 0.9.4 under Mac OS Catalina 10.15.4 with very few problems - mostly of my own making!
i.e managed to duplicate a part but still had the same id so an error occurred - easily fixed !
Also trying to add a strip board for prototyping with more rows and/or columns than the standard set size seem to provoke a memory attack of the rainbow spinning ball and it slows to a snails pace.
So what actually happens on your machine after a double click - something must happen albeit that it launches and quits immediately with no warning. Almost sounds like a corrupt support file - plist or similar. Maybe a complete deinstall using an app such as ‘ApplCleaner’ (free of course) to make sure all remnants of the old version are removed and then a clean install again might help!
PLEASE - make a backup of parts database and your own first!
I did a full uninstall with CleanMyMac and then re-install from scratch, now have it all running…
Any idea what it was unhappy about on the first installation? Although we now know to suggest trying a delete and reinstall for future cases.
Peter
I do not know, I have not been able to replicate…
I’ve had this happen many times when upgrading various applications and its nearly always been corrupt support files. I use the app cleaner method because it can find associated files which may not have the app name in it - developers get up to all sorts of tricks sometimes to protect their app.
Also Apple have changed so many permissions for security in the latest OS which may have contributed to the issue!
Glad its all ok now!