Learning Locker configuration on VPS / CENTOS 6

General information for the business: Learning locker installed on VPS via SSH but configuration isn't quite right (giving 500 errors)
Description of requirements/functionality: Having followed the learning locker installation instructions here:
https://gist.github.com/davidpesce/7d6e1b81594ecbc72311 and here:
http://docs.learninglocker.net/installation/

The only errors/warnings I get are ones that I am assured can be ignored. The VPS is running on CENTOS 6 and cannot be upgraded at this time. It also has WHM / CPanel installed and this cannot be removed or altered at all as there is a live site relying on it at the moment.

Anything done must not affect this live site.

On going to http://mydomain.com/learninglocker/public I get a 500 error instead of what should be there. This happened on a previous set up with CENTOS 7, but was able to be resolved by correcting the configuration.
Specific technologies required: Linux, MongoDB, CENTOS6
OS requirements: Linux
Extra notes: The live site must not be affected by any actions, except for being offline briefly if the server needs rebooting.
I can deal with the security key error once the 500 error is resolved.