Why doesn't reCaptcha work in Firefox with .rf domains?

Question

Domain name market

Hello. Got a google recaptcha
account . Created a captcha, configured: Placed the code on the sites in accordance with the docks. In chrome it works fine, but in firefox it gives "Invalid domain for site key" . To check the captcha itself, I found a page with an example of a plugin for wordpress , on which there are no errors. In this connection, I came to the conclusion that the captcha has a problem with .rf domains. I googled, I did not find the right answer, so I decided to write here, maybe someone faced a problem.