This appears to be a bug caused by the Mac System Integrity Protection and not the fault of Crowd Render, as other plug-ins may not work either. If you can install CR, but cannot enable it without an error, this may be the cause.

Go into the recovery manager while your Mac boots up “Command-R”. Then go into the terminal and type “csrutil disable” and then hit return. Reboot and see if Blender add-ons are working.

If this is indeed the problem, it would be a Blender bug they need to fix. It appears to be some type of permissions related error.