Your cron job could be already running after you send the request, but because Cloudflare has a 100 second timeout, if there’s no respond from your server within 100 seconds, Cloudflare will simply return Error 524 to you.
If you require a response to be returned from your server to read the job status, then there’s nothing we can help with (unless you are using Enterprise plan which can increase the timeout to 600 seconds) except unproxying the DNS record. Otherwise, you can simply ignore it.