These errors are not related to the plugin, maybe it's better talk to your webhost or directly with cloudflare (open a support ticket).
- 404 errors: only occurs when something is not found on your server/hosting account. It's not related to Cloudflare.
- 500 error: internal server error, something is wrong with your server.
- 502 or 504 errors: contact Cloudflare - https://support.cloudflare.com/entries/22052913
- "website offline" error: https://support.cloudflare.com/entries/22036452