Hi y’all, an update! We have now released a notarized build of Axure RP 9 that should help with the new security prompts that were showing up for 10.15 users and preventing launch. You can download that notarized build of Axure RP 9 (build 3665) here. This new build should give you the option to launch the app right from the dialog that pops up when you try to launch on 10.15 for the first time. If that doesn’t do the trick, then please open “System Preferences > Security & Privacy > General” and ensure that your settings are set to allow apps from the “App store and identified developers” to open if you haven’t already. And of course if you still run into trouble, please go ahead and email support@axure.com and let us know what steps you’ve taken thus far. Thank you! 
Update on the update: the live Mac builds on our site at www.axure.com/update and for our release candidate page, www.axure.com/release-candidate, have been updated to the notarized builds that should launch on macOS 10.15. Feel free to use those normal links going forward!