EZ Forms - ReCaptcha not working

Hi there,
I’m struggling since 1 week on the ReCaptcha setup with the EZ Form plugin. I’ve frontend running on port 3000 and strapi on 1337 in my localhost.

captchaProvider: { name: 'none'}
the submission works fine and data are stored on strapi.

With the captha enabled and set I get a generic 500 error.

Any suggestion?