Reposting my answer from this forum thread: https://www.telerik.com/forums/just-downloaded-fiddler-everywhere---mac
While Fiddler Everywhere is not compatible with some VPN tools, it does not makes sense that it fails to start. Most likely, you will see a login error due to some endpoints being unreachable through the VPN, but the application remains active. Check if you have access to the required endpoints from our prerequisites. Alternatively, you can also use the following endpoint to verify that you can access the Fiddler Everywhere endpoints: https://fiddler-backend-production.s3.amazonaws.com/connectivity-test/check-fe.html
You can also privately send us the Fiddler Everywhere log files to support at getfiddler.com. Refer to this KB article on how to access the logs manually. Note that these logs might contains sensitive personal data, so do not post them in public forums.
It looks like this is resolved. I don't know what specifically fixed this. Possibly a reboot of the machine. Not sure. I don't need to send the logs.
Still getting error, sending logs to support at getfiddler
Now working, seems to be hit or miss. Enterprise proxy and vpn messing up the app. But I think I have a work-around. Thanks for info.
When I launch Fiddler Everywhere 3.3.1
Nothing happens it tries to start, says loading in the prompt then crashes.
I am trying to do the trial
MacBook Pro (15-inch, 2017)
16 GB 2133 MHz LPDDR3
Catalina - 10.15.7 (19H1922)
It looks like it takes about 2-3 minutes to startup...still fails
I am also on a company VPN, could be related.