Google reCAPTCH not working with registration form

We recently installed the cloud_captchas plugin and set up Google reCAPTCHA. It works when creating an Indico profile, but not when filling out the event registration form. I fill in all the information, check the “I’m not a robot” checkbox, and click 'Register”. It resets the Captcha checkbox again, coming as a required field. I have everything running as Docker. I don’t see an error in the log files.

We use Indico v3.3.8.

Cloud CAPTCHAs v3.3.2