Why is recaptcha not showing up through a proxy server?

Question

proxy

Good afternoon!
I have such a problem. Through a proxy server, recaptcha is not displayed on sites. For example, on the website of the filing cabinet of arbitration cases. There, when you click the "Find" button in the browser console, it displays the error "Uncaught Error: ReferenceError: grecaptcha is not defined". I dug into the code of the page, found a mention of Google's recaptcha. Tried to whitelist google.com, gstatic.com, but nothing helps.
Tell me, please, in which direction to dig.