Cloudflare's Bot Fight Mode is blocking webhooks sent from ClickUp. Since, ClickUp doesn't used dedicated IP ranges for these, the only way to allow it through is to whitelist the ASN associated with the request, which whitelists all requests from that ASN which isn't ideal.

ClickUp can create a verified bot to prevent this issue by submitting the info to Cloudflare. Details are here: https://developers.cloudflare.com/bots/troubleshooting/#i-run-a-good-bot-and-want-for-it-to-be-added-to-the-allowlist-cfbot_managementverified_bot-what-should-i-do