Hi, I'm having this problem in El Capitan 10.11.4 I was previously able to run the itch app, so not sure what has changed. Have re-installed but same result.
Here's the relevant part from the console log:
02/05/2016 11:33:14.305 lsd[316]: LaunchServices: Could not store lsd-identifiers file at /private/var/db/lsd/com.apple.lsdschemes.plist
02/05/2016 11:33:14.309 lsd[316]: LaunchServices: Could not store lsd-identifiers file at /private/var/db/lsd/com.apple.lsdschemes.plist
02/05/2016 11:33:14.323 com.apple.xpc.launchd[1]: (com.apple.xpc.launchd.oneshot.0x10000015.Electron[12666]) Could not find and/or execute program specified by service: 2: No such file or directory: /Applications/itch.app/Contents/MacOS/Electron
02/05/2016 11:33:14.323 Dock[319]: spawn_via_launchd() failed, errno=111 label=[0x0-0x219219].io.itch.mac path=/Applications/itch.app/Contents/MacOS/Electron flags=1 : LaunchApplicationClient.cp #963 LaunchApplicationWithSpawnViaLaunchD() q=com.apple.root.default-qos
02/05/2016 11:33:14.323 Dock[319]: spawn_via_launchd() failed, errno=111 label=[0x0-0x219219].io.itch.mac path=/Applications/itch.app/Contents/MacOS/Electron flags=1
02/05/2016 11:33:14.324 Dock[319]: LSOpenFromURLSpec(file:///Applications/itch.app/) failed with -10810
02/05/2016 11:33:14.331 lsd[316]: LaunchServices: Could not store lsd-identifiers file at /private/var/db/lsd/com.apple.lsdschemes.plist