I installed Mono 4.2.4 (newer version of Mono didn't work at all) and installed Fiddler in a folder I have write access to. I followed the instructions for syncing Fiddler and am able to successfully start Fiddler. However, each time I click the File --> Capture link, I get the following pop-up:
osascript wants to make changes.
Touch ID or enter your password to allow this.
I enter my password, and it is accepted, but still no traffic is captured. When I click the capture link again, I get the same pop-up.