Hi all
The problem has been solved! Thank you all for your input.
Solution:
If you are on a shared hosting plan and you have a 3rd party anti-malware company that uses a CDN to route your traffic through, checking for malware before going to the server. The firewall caching is the problem.
The caching level on the securi firewall was set to 'enabled' by default. This will cause session issues for Moodle.
Change the caching level to 'site caching'. This caching level will respect the headers sent by Moodle. It may cache the page content if Moodle sends the no-cache header.
Thank you all,
Adam