ContactForm_Widget recaptcha response success is always false

when using the “Spam Protection” “Recaptcha” option I always get “Error validating your Captcha response”.

I tried sowhat everything. Changing the wp_remote_post to a getfilecontents, to a curl post,… but the “succes” result is always false.

When calling the “https://www.google.com/recaptcha/api/siteverify” url directly in the browser of through postman the “succes” variable is true.

Does someone know whats wrong?