Often at time, mod_security rule sets could be preventing normal web application procedures and requires the rule to be disabled/whitelist.
1. Log into WHM as root
2. Select "ModSecurity Tool" under Security Center
3. Click "Rule List" on the right hand corner
4. Enter the Rule ID, for an example: "33342" and then click the magnifying glass to start the search and click "Disable"
Note: You will be able to locate the Rule ID by checking into your Apache's error log: