Agents or users are repeatedly asked to fill out CAPTCHA requests when using the help center.
Are you accessing Zendesk through a proxy?
If access to your help center is through a proxy, you are more likely to receive a CAPTCHA challenge as your request will look more like an automated request than one made by a user directly over the Internet.
For more information, see this article: Accessing Zendesk with a reverse proxy. If it is not feasible to access Zendesk without a proxy, follow the remediation steps to decrease the chances of your proxy setup triggering Bot Management.
Cloudflare Privacy Pass
If the issue persists, Zendesk recommends installing the Privacy Pass browser extension for Chrome and Firefox. This decreases the frequency of CAPTCHA challenges by generating 30 tokens every time a challenge is solved. For more information about the Cloudflare Privacy Pass, see this article from Cloudflare's help center: Using Privacy Pass with Cloudflare.
For related information, see this article: CAPTCHA FAQs.