I updated to the newer version of OSX. Factorio booted up just fine. Thanks for the help!

Thanks. It definitely sounds like that. I'll update OSX and try again. If that doesn't work I'll try to go back a version.

I am on a Mac and using steam. I was just playing yesterday with no issues. Today I go to boot the game and when it hits 98% it pops up with an error. I reboot computer, same thing. I uninstall and reinstall through steam, no change.

Here is the error
"Unexpected error occurred. If you're running ...