Hi there,

Thanks for writing to Cloudflare Support.

A 4xx Client Error is a client side error that means that the client sent something the origin was unable to process. Cloudflare does not generate any 4xx error code, so this would indicate something is not configured correctly with your hosting provider or your client is sending something incorrect. The best next steps would be to have this client generate a HAR file and send this to your hosting provider to identify what potential misconfiguration could be in place.

This is an automated response which we hope has answered your question. If you need further assistance, simply reply to this email to reach a Cloudflare Technical Support Engineer. Please note that it will likely take a few days before we can respond to your ticket through here; you may receive faster support by using our Knowledge Base, Community forums or by upgrading your zone to a paid plan and then resubmitting your ticket to receive priority support.

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