reCaptcha extension not working in China

Hello,

we’ve deployed the free reCaptcha extension for Ultimate Member in a site, and everything was working correctly. However, this is a worldwide association, and there are many members in China. We were notified this week that the registration form wasn’t working correctly there (people were not able to register), and apparently the problem is caused because of Google being banned in China, which makes the reCaptcha not to work there.

Are there any alternatives to reCaptcha to be added to the forms? If so, how?

Thank you in advance.
Andrés

The page I need help with: [log in to see the link]