Neon on Mac 10.12.5 (Sierra). I was using Neon for awhile, then it started crashing on me. I uninstalled and reinstalled multiple times to no avail. I kept searching for answers, and tried resetting the creation and modification dates as suggested elsewhere. But that didn't work. Then I thought it must be a plist problem. I downloaded a program (PlistEdit Pro) and and checked all of Neon's plist settings. I found that there were four (4) info.plist files. The first one was fine, but when I checked the others, the CFBundleSignature key was showing "????" (without the quotation marks) on all three. On the first file, the value for that key was "l33t" (again, without the quotation marks). So I changed the values for that key in the other plist files to that same value, saved each file, and double-clicked Neon and it worked. HTH. YMMV. Messing with plist keys and values is dangerous. Do so at your own risk.