Awesome, that seems to have worked, thank you Elaine! On 8/28/20, 3:40 PM, "Elaine Meng" <meng@cgl.ucsf.edu> wrote: Hi Dave, This is caused by security changes in Catalina. The workaround (also shown in red text on the download page) is: To start Chimera on 10.15 (Catalina) or later, you need to right-click (or alt-click) on the app icon and choose "Open" from the popup menu. This is only necessary the first time you use it. Thereafter it can be started normally. I hope this helps, Elaine ----- Elaine C. Meng, Ph.D. UCSF Chimera(X) team Department of Pharmaceutical Chemistry University of California, San Francisco > On Aug 28, 2020, at 11:28 AM, David Butler <dbutler@FL63inc.com> wrote: > > Hi > I get the error attached when trying to install the stable version of the software. > My OS is Catalina 10.15.6 > Thanks > Dave Disclaimer The information contained in this communication from the sender is confidential. It is intended solely for use by the recipient and others authorized to receive it. If you are not the recipient, you should delete this message. You are hereby notified that any disclosure, copying, distribution or taking action in relation to the contents of this information is strictly prohibited and may be unlawful.