Sounds like either what ever user your web server runs as doesn’t have permission to read/write the Mason cache files under
/var/cache/request-tracker4/mason_data or if you have SELinux turned on its interfering with the process.
Easiest to check the first one: find out what user your web server is running as (usually something like
www) and then as root do:
chown -R webserver_username /var/cache/request-tracker4/mason_data
webserver_username is whatever user name you found from the web server config.
If that doesn’t fix it, and you do have SELinux installed, try as a test:
as root. If things then start working its an SELinux rights problem.