If something breaks in wp-admin or on the front end after enabling protection, disable the firewall briefly to confirm it is the cause.
- Go to Security Ninja → Firewall.
- Click Disable Firewall.
- Retry the action that failed.
- When finished testing, enable the firewall again and save the secret access URL if you have not already.
If disabling fixes the issue, contact support with what you were doing when it failed. Also see Cannot import data for import-plugin conflicts.