To add to the answer, the solution would appear to be found in the following link:
https://www.propellerheads.se/support/u ... -reason-9/https://www.propellerheads.se/support/user/reason/mac-troubleshooting/where-are-the-sound-banks-in-reason-9/
The folder in question in application support should be deleted in order for Reason 9 to launch. This should fix the issue.